
Book yG % , 



THE 



HAND-BOOK 



HOUSEHOLD SCIENCE. 



A POPULAE ACCOUNT OP 



HEAT, LIGHT, AIR, ALIMENT, 
AND CLEANSING, 'Ir/ 

•an 
THEIR SCIENTIFIC PRINCIPLES AND DOMESTIC APPLICATIONS. 

WITH NUMEKOUe ILLUSTEATIVE DIAGEAMS. 



BY 

EDWARD L. YOUMANSjM.D., 

AUTHOR OP 
"TUK CLASS-BOOK OF CnEMISTKT," "OnKSIIOAL ATLAS," "CHAKT," &C. 



NEW YORK: 
D. APPLETON & CO., 443 & 445 BROADWAY. 

LONDON: IC LITTLE BRITAIN. 
1864. 



Enteeed according to Act of Congress, in the year 1857, hj 

T>. APPLETON & CO., 

In the Clerk's Office of the District Court of the United States for the 

Southern District of New York. 



^:^° An edition of the present work has been issued, 
arranged with Questions for the use of Academies^ Semi- 
navies^ and Schools. 






CONTENTS. 



PART I.— HEAT. 

PAGX 

PREFACE, 7 

INTRODUCTION, 11 

I. Sources axd Distribution op Terrestrial Heat, .... 17 

II. Influence of Heat upon the Living World, .... 19 

III. Measurement op Heat — The Thersiometer, 23 

IV. Radiation and its Effects, 27 

V. Conduction of Heat, and its Effects, . . . . . .34 

VI. Heat conveyed bt moving Matter, .... 36 

VII. Various properties and effects of Heat, ... 37 

VIII. Physiological effects op Heat, 48 

IX. Artificial Heat — Properties op Fuel, 49 

X. Air-cureents — Action and management op Chimneys, ... 55 

XI. Apparatus op Warming, 60 

1. Open fireplaces, 62 

2. Stoves, 67 

3. Hot-air arrangements, 70 

PART II.— LIGHT. 

I. Nature of Light — Law of its Diffusion, 76 

II. Reflection of Light, 79 

III. Transmission and Refraction of Light, 82 

,■' rV. Theort op Light — Wave movements in Nature, .... 84 

' V. Composition and mutual relation op Colors, 88 

.' V'l. Practical suggestions in combining Colors, .... 102 



IV CONTENTS. 

PABa 

VII. Production of Artificiai. Light. 

1. The Chemistry of Illumination, .... . 105 

2. Illumination by means of Solids, .... 108 

3. Illumination by means of Liquids, 112 

4. Illumination by means of Gases, 11a 

5. Measurement of Light, 12A 

V'lII. Structcrb and Optical powers of the Ete, 126 

IX. Optical defects of Vision — Spectacles, 131 

X. Injurious action of Artificial Light, 137 

XI. Management of Artificial Light, 146 

PART III.— AIR. 

I. Properties and composition of the Atmosphere, .... 150 
II. Effects of the constituents of Air. 

1. Nitrogen, 154 

2. Oxygen, 154 

3. Moisture, 157 

4. Carbonic acid, 161 

5. Ozone and electricity, 164 

III. Condition of Air provided bt Nature, 165 

IV. Sources of impure Air in Dwellings, 168 

V. Morbid and fatal effects of impure Air, 174 

VI. Rate of contamination within doors, 181 

VII. Air in Motion — Currents — Draughts, 185 

VIII. Arrangements for Ventilation, 193 

PART IV.— ALIMENT. 

I. Source of Aliments — Order of the subject, 205 

II. General properties of Alimentary Substances. 

1. Principles containing no Nitrogen. 

A Water, ... 20i' 

B The Starches, 2n 

C The Sugars, 216" 

D The Gums, 223 

E The Oils, 223 

F The Vegetable Acids, 225' 

2. Principles containing Nitrogen. 

A Vegetable and Animal Albumen, 227 

B Vegetable and Animal Casein, 228 

C Vegetable and Animal Fibrin, 228 

D Gelatin, 230 



CONTENTS. y 

PA.6> 

a Compound Aliments— Vegetable Foods, 

A The Grains, 231 

B Leguminous Seeds, 241 

C Fruits, 243 

D Leaves, Leafstalks, etc., 244 

E Roots, Tubers, Bulbs and Shoots, 245 

4. Compound Aliments — Animal Foods. 

A Constituents of Meat, 248 

B Production and composition of Milk, .... 250 
IIL Cplinart Changes of Alimentary Substances. 

1. Combining the elements of Bread, 256 

2. Bread raised by Fermentation, 259 

262 

. 267 
271 

. 274 
277 

. 281 
285 

. 287 



8. Properties and action of Yeast, . 

4. Raising Bread without Fermentation, 

5. Alterations produced in baking Bread, 

6. Influence of foreign substances upon Bread, . 

7. Vegetable Foods changed by boiling,. 

8. How cooking changes Meat, .... 

9. Preparation and properties of Butter, 
10. Preparation and properties of Cheese, . 

rV. Common Beverages. 

1. Properties and preparation of Tea, 289 

2. Properties and preparation of Coffee, 293 

3. Cocoa and Chocolate, 298 

V. Preservation op Alimentary Substances. 

1. Causes of their Changeableness, 300 

2. Preservation by exclusion of Air, 302 

3. Preservation at Low Temperatures, 305 

4. Preservation by Drying, ..%.... 309 

5. Preservation by Antiseptics, 311 

6. Preservation of Milk, Butter, and Cheese, . . . 314 
VL Materials of Culinary and Table Utensils, 318 

VII. Physiological effects of Food. 

1. Basis of the demand for Aliment, 324 

2. Digestion — Changes of food in the Mouth, .... 330 

3. Digestion — Changes of food in the Stomach, . . . 335 

4. Digestion — Changes of food in the Intestines, . . . 344 

5. Final destination of Foods, 347 

6. Production of Bodily Warmth, 353 

7. I'roducfion of Bodily Strength, 360 

1 



VI CONT32NTS. 

PAG« 

8. Mind, Body, and Aliment, ... ... 364 

9. Influence of Special Substances. 

A Saline Matters, 369 

B Liquid Aliments, 374 

C Solid Aliments 383 

10. Nutritive value of Foods, 392 

11. The Vegetarian Question, 402 

12. Considerations of Diet, ....... 408 

PART v.— CLEANSING. 

I. Peincipal Cleansing Agents, ........ 422 

II. Cleansing of Textile Articles, 428 

III. Cleansing of the Pekson, 431 

IV. Cleansing of the Aib, 436 

V. Poisons, • 441 

APPENDIX, 443 

INDEX, . 445 



PREFACE. 



A DESIRE to prepare a better statement than has hitherto 
been offered, of the bearings of science upon the economy of 
the household, has led to the following work. The purpose 
has been, to condense within the limits of a convenient manual 
the largest possible amount of interesting and valuable scien- 
tific information of those agents, materials, and operations in 
which we have a concern, chiefly as dwellers in houses. 

The subjects are treated somewhat in an elementary way, 
but with constant reference to their domestic and practical 
relations. Principles are universal; their applications are 
special and peculiar. There are general laws of light, heat, 
and air, but they may be studied in various connections. 
There are many things about them which a person, as a resi- 
dent of a house, cares little to know ; whUe there are others 
In which he has a profound interest. To consider these, we 
assume to be the province of household science. The question 
of moisture in the air, for example, is one of universal scien 
tific interest to meteorologists ; but it has also a special antl 
vital import for the occuj)ants of stove and furnace heated 
rooms. Different colors, when brought together, alter and 
modify each other according to a simple and beautiful law 
and the Painter, the Decorator, and the Dyer, have each s 
technical interest in the principle ; but hardly more than ihi 
Lady at her toilette or engaged in furnishing her house. Thi 
Agriculturist is interested in the composition of food, as a 
producer; the Householder equally, as a consumer. Thn 



Vm PREFACE. 

Doctor must know the constituents of air and its action upon 
the living system for professional purposes, and he studies 
these matters as parts of his medical education ; but for the 
same reasons of life and death, the inhabitants of houses are 
concerned to understand the same things. 

These examples illustrate the leading conception of the 
present work. Its jireparation has been attended with grave 
difficulties. Of course, a volume of this compass can present 
only a compend of the subjects it considers. Heat, light, air, 
and aliment are topics of large extent, wide and complex in 
their i^i-inciples, which are of boundless apjili cation. We do 
not profess to have treated them with any completeness, 
but only to have brought distinctly forward those aspects 
which have been formerly too much neglected. In deciding 
what to state, and what to omit, we have been guided by two 
rules ; firsts to present such facts and principles as have the 
directest bearing upon household phenomena ; and, second, to 
bring into prominence many important things not found in 
common books nor included in the ordinary range of school 
study. As elementary principles may be found fully treated 
elsewhere, we have been brief in their statement, thus gaining 
opportunity for important hints and views not generally acces- 
sible. Our chemistries are deficient in information of the 
composition and properties of food, while the physiological 
class-books are equally meagre in statements of its effects ; 
we have accordingly dwelt upon these points with something 
of the fulness which their importance demands. So with 
heat, hght, and air. It is hoped that the following pages wiQ 
vindicate the fidelity with which we have labored to enrich the 
v'olume with new and valuable facts and suggestions, not pro- 
curable in our family manuals or school class-books. Many 
of the subjects presented have recently undergone searching 
investigation. They are rapidly progressive ; facts are multi- 
plying, and views widening. We have si:)ared no pains to 
give the latest and most authentic results. Although the vol- 
ume is to a great extent self-explanatory, and adapted for 
family and general reading, yet in the proper order of school 



PEEFACE. Vt 

study it will find its most appropriate place after a course of 
elementary lessons in chemistry and physiology. 

We have striven to present the subject in such a manner 
as to make reading and study both agreeable and instructive. 
Technical terms constitute a formidable obstacle, on the part 
of many, to the i^erusal of scientific books. This is a veiy 
serious difficulty, and requires to be managed as best we can. 
In works designed for general use they should be avoided as 
far as possible, and yet it is out of the question to think of 
escaiDLng them entirely. If we would enjoy the thoughts of 
science we require to learn at least a portion of the language in 
which alone these thoughts are conveyed. The new objects 
and relations must be named, or they cannot be described and 
considered. We have stiidiously avoided obstructing the 
course of the common reader with many technical words, yet 
there are some which it was impossible to omit. The terms 
carbon, oxygen, hydrogen, nitrogen, carbonic acid, and some 
others, though hardly yet familiarized in popular speech, must 
soon become so. They are the names of substances of univer- 
sal interest and importance ; the chief elements of air, water, 
food, and organized bodies by which Providence carries on 
the mighty scheme of terrestrial activity and life. They are 
the keys to a new dej)artment of intellectual riches — the latest 
revelation of time respecting the conditions of human exist- 
ence. The time has come when all who aspire to a character 
for real mteUigence, must know something of the objects 
which these terms represent. 

As respects the body of its facts and principles, any Avork 
of this kind must necessarily be of the nature of a compilation. 
We make no claim to discovery. The materials of the volume 
— the result of laborious and life-long investigations of many 
men — ^have been gathered from numberless sources, — from 
standard books i;pon the various topics, scientific magazhies, 
original memoirs, personal correspondence, observation, house- 
hold experience and laboratory examinations. Constant refer- 
ence is made to authorities followed, and the language of 
others employed whenever it appeared to convey the most 



X PREFACE. 

suitable statement. Exemption from errors can hardly be 
expected in a work of this kind — errors of oversight and 
errors of judgment. Besides, many of its questions are in an 
unsettled state and involve conflicting views. Yet the utmost 
care has been taken to make an accurate and rehable presenta- 
tion of the subjects considered. 

The Author desires to acknowledge his indebtedness to 
his sister, Eliza A. YouMAifs, for constant and invalua- 
ble aid in the preparation of the work, not only in various 
experimental operations incident to its progress, but also in 
several parts of its Uterary execution. To his friend Mr. 
Richard H. Manning, who, though engaged in absorbing 
mercantile j)ursuits, has yet found time for thought in the di- 
rection of science and its applications, his thanks are due for 
valuable suggestions and important manuscrij)t corrections. 

If the work shall serve, in however small a degree, to ex- 
cite thought, to give additional interest to household phe- 
nomena, and awaken a stronger desire for domestic improve- 
ment, the labor of its preparation will not have been perfonned 
in vain. 

New Yoek, August, 186T. 



INTKODUCTION. 



"Wheit a work is presented, claiming place in a systematic course of 
school study, two questions at once arise in the mind of the discrimi- 
nating educator : first^ what is the nature, rank, and value of the 
knowledge it imparts ? and, second, what will be its general influence 
upon the mind of the student ? In this twofold connexion there are 
some thoughts to which we solicit the reader's earnest and considerate 
attention. 

The present volume has been prepared under a conviction that the 
knowledge it communicates is first in the order of importance among 
things to be considered by rational and civilized people. "Every 
man's proper mansion-house and home," says Sir Henet "Wotton, 
" is the theatre of his hospitality, the seat of self-fruition, the com- 
fortablest part of his own life, the noblest of his son's inheritance, a 
kind of private princedom ; nay, to the possessors thereof an epitome 
of the whole world." Nothing needs to be added in eulogy of the 
household home, the place of life's purest pleasures and sweetest ex- 
periences, the perpetual rallying point of its hopes and joys. What- 
ever can render it more pleasant or attractive, or invest it with a new 
interest, or in any way improve or ennoble it, is at once commended 
to our sympathy and regard. To consider all the agencies which in- 
fluence the course and character of household life, is far from the ob- 
ject of the present work. Our concern is chiefly with its more mate- 
rial circumstances and conditions. That we should understand some- 
thing of the wonderful physical agencies which have control of our 
earthly being, and which are so incessantly illustrated in the dwelling, 
and be at least partially acquainted with those fixed natural ordi- 
nances upon which our daily welfare, comfort, health, and even life, 
immediately depend, must certainly be acknowledged by all. One of 
the most starthng facts of man's history is, that placed in a world of 
immutable order, and endowed with such exalted gifts of understand- 



XU INTKODUCTION. 

ing and reason, lie should yet have contrived to maintain so dense and 
perfect an ignorance of himself and the familiar objects by which ho 
is surrounded. That exact knowledge of the ways of nature which puts 
her powers at human command, and bears the daily fruit of substan- 
tial improvement and universal beneficence, would seem to be the last 
and noblest achievement of mind; a fruition of long intellectual 
growth, the highest form in the latest time, after the preliminary and 
preparatory experience of ages. In its earlier strivings we observe 
the mind of man intently occupied with itself, and regarding material 
nature with unutterable disdain. It wandered aimless and dissatisfied 
in the misty regions of speculaticn. Its first great conquest was in 
the realm of abstraction, farthest removed from the vulgarities of 
mere matter — the discovery of mathematical principles. The earliest 
application of thought to physical subjects was away in the distant 
spheres, where imagination had revelled wildest from immemorial time, 
to the luminous points and mysterious movements of the heavens, 
which, according to Plato, were most admirably fitted to Ulustrato 
geometry. The skies were mapped and charted long before the earth. 
Copernicus struck out the grand law of celestial circulation before 
Harvey discovered that of the blood. The genius of Newton flashed 
an immortal light iipon the mechanism of the universe, many years 
before Rumford began his humbler domestic investigations. Centuries 
have passed since the establishment of universal gravitation, while 
there are men now living who may recollect the most gigantic stride 
of modern science, the discovery of oxygen gas by Priestly, and the 
earliest analysis of the air we breathe. Chemistry, which is the name 
given to the first serious grappling of human intelligence with all 
forms of common matter, belongs chiefly to our own century. This, 
too, has been progressive, and in its course has conformed to the gen- 
eral law we are indicating. Its earliest investigations were directed 
to inert mineral substances, stones and rocks ; while the formal and 
systematic elucidation of those conditions and phases of matter in 
which we have the deepest interest — vegetable and animal compounds 
and processes, agricultural, physiological, and dietetical chemistry — is 
eminently an affair of our own day. Thus, the spirit of inquiry, at 
first recoiling from matter, and circling wide through metaphysical 
vacuities, gradually closed with the physical world, and now finds its 
last and highest inquest into the material conditions of man's daily 
life. The course of knowledge has been expansive, as well as pro- 
gressive; from narrow views to universal principles; from empty 
Bpeculations to world-wide utilities; from the pleasure of a few to 



INTKODUCTION. , XIU 

the advantage of the many ; from utter ignorance and contempt of 
nature, to the revelation of all-embracing laws, and a beautiful and 
harmonious order in the commonest objects and operations of daily 
experience. To the truth of this general statement, the existence of 
the present book may be taken as a strong attestation. The mass of 
its facts and principles are the result of recent investigation. A 
hundred years ago such a work would have been, in all its essential 
features, a blank impossibility ; indeed, it had lacked its richest mate 
rials if prepared for the last generation. 

These facts should not be without their influence upon the schemt 
of popular education. It is its first duty to communicate that infor- 
mation which can be reduced to daily practice, and yield the largest 
measure of positive good. If recent inquiry has opened new treasures 
of available truth, it is bound to take charge of them for the genei'al 
benefit. It must report the advance of knowledge, and Keep pace 
with the progress of the human mind, or it is false to its trust. The 
subjects of study should be so modified and extended as to afford the 
largest advantage, intellectual and practical, of the labors of the great 
expounders of nature, — especially in those departments where knowl- 
edge can be made most useful and improving. A rational and com- 
prehensive plan of education for all classes, which shall be based upon 
man's intrinsic and essential wants, and promptly avail itself of every 
new view and discovery in science, to enlighten him in his daily rela- 
tions and duties, is the urgent demand of the time. Nor can it be 
always evaded. We are not to trundle round for ever in the old ruts of 
thought, clinging with blind fatuity to crude schemes of instruction, 
which belong, Avhere they originated, with the bygone ages. He who 
has surrendered his life to the inanities of an extinct and exploded 
mythology, but who remains a stranger to God's administration of 
the living universe ; who can skilfully rattle the skeletons of dead lan- 
guages, but to whom the page of nature is as a sealed book, and her 
voices as an unknown tongue, is not always to be plumed with the 
supereminent designation of ' educated.' 

There are many things, unquestionably, which it would be most 
desirable to study : but opportunity is brief, and capacity limited ; 
and the acquisition of one thing involves the exclusion of another. We 
cannot learn every thing. The question of the relative rank of vari- 
ous kinds of knowledge — what shall be held of primary importance 
and what subordinate, is urgent and serious. As life and Iiealth are 
the first of all blessings, to maintain them is the first of all duties, 
and to understand their conditions the first of mental requirements. 



XIV - INTEODUCTION. 

Sliall the thousand matters of mere distant and curious concernment 
be suffered to hold precedence of the solemn verities of being which 
are woven into the contexture of familiar life ? The physical agents 
which perpetually surround, and act upon, and within us, hent, light, 
air, and aliment, are liable to perversion through ignorance, so as to 
produce suffering, disease, and death; or they are capable through 
knowledge of promoting health, strength, and enjoyment. What 
higher warrant can be asked that their laws and effects shall become 
subjects of general and earnest study. It may seem strange that in 
regard to the vital interests of life and health, man should be left 
without the natural guidance of instinct, and be driven to the necessity 
of reflection and study ; that he for whom the earth seems made 
should be apparently less cared for in these respects than the inferior 
animals. Nevertheless, such is the divine ordination. Neither our 
senses, instincts, nor uninstructed faculties are suflacient guides to good, 
or guards from evil, in even the ordinary conditions of the civilized 
state. Things which most deeply affect our welfare, the senses fail to 
appreciate. They can neither discern the properties nor the presence 
of the most deadly agents. The breathing medium may be laden with 
noxious gases to the peril of life, and the senses fail to detect the dan- 
ger. Hunger and thirst impel us instinctively to eat and drink, but 
they fail to inform us of the nutritive value of alimentary substances 
or their dietetical fitness to our varying requirements. For all those 
things which are independent of man's will, Providence has taken 
abundant care to provide ; while in the domain of voluntary action, 
blind instinct is replaced by rational forecast. "Whatever may have 
been those original conditions of bare animal existence which some 
yet sigh for, as the ' true state of nature,' we are far removed from 
them now. They have been successively disturbed as, generation 
after generation, intelligent ingenuity has been exercised to gain con- 
trol of natural forces for the securing of comforts and luxuries, and 
to liberate man from the privations and drudgeries of the uncivilized 
condition. But unmingled good seems not permitted ; the benefits are 
alloyed with evil. Thus, the introduction of the stove, while afford- 
ing the advantage of economy and convenience in the management 
of fire, was a step backward in the matter of ventilation. Gas- 
lighting was a great advance on the methods of artificial illumination, 
but there came with it augmented contamination of the breathing 
medium and new dangers to the eyes. Against these and similar in- 
cidental mischiefs — ' residues of evil ' that accumulate against the pre- 
dominating good, there is no other protection than intellect, instructed 



mTRODucnoN. rv 

in the material conditions which influence our health and life, for 
these, and kindred considerations of practical moment to all who oc- 
cupy dwellings and assume civilized relations, we urge the study 
of Tiousehold science as an essential part of general education. 

It deserves to be better understood, that the highest value of science 
is derived from its power of advancing the public good. It is more 
and more to be consecrated to human improvement, as a sublime re- 
generative agency. Working jointly and harmoniously with the great 
moral forces of Christian Civilizatiop, we believe it is destined to eftect 
extensive social ameliorations. That it is not yet fuUy accepted in this 
relation is hardly surprising. The work of presenting scientific truth 
in those forms which may best engage the popular mind, is not to bo 
fairly expected of those who give their lives to its original development. 
There is a deep satisfaction, an intrinsic compensating interest to the 
discoverer in the naked quest of truth, which is largely independent of 
any utility that may flow from the inquiry. In the exalted conscious- 
ness of achievement, the man of science finds an intellectual remunera- 
tion, 80 royal and satisfying that other considerations have compara- 
tively little weight. Hence the inditference, to a great degree inevi- 
table, with which original explorers contemplate the reduction of sci- 
entific principles to practical use. Moreover, this utter carelessness of 
results, where the mind is not biased, nor the vision blurred by ulterior 
considerations, is far the most favorable for successful investigation. 
Conscious that the effects of his labors are finally and always beneficial 
in society, the enthusiast of research may be excused his indifference 
to their immediate reception and uses. But the formal denial that the 
allegiance of mind is supremely due to the good of society is quite 
enother affair. The sentiment too widely entertained in learned and edu- 
cational circles, that knowledge is to be firstly and chiefly prized for its 
own sake, and the mental gratification it produces, we cannot accept. 
The view seems narrow and illiberal, and is not inspired of human sym- 
pathy. It took origin in times when the improvement of man's con- 
dition, his general education and elevation, were not dreamed of. It 
came from the ancient philosophy, which was not a dispensation of pop- 
ular beneficence, an all-diffusive, ennobling agency in society, but con- 
fessed its highest aim to be a personal advantage, shut up in the indi- 
vidual soul. It was not radiant and outflowing like the sun, but drew 
all things inward, engulfing them in a malstrom of selfishness. 

The baneful ethics of this philosophy have given place to the higher 
and more generous inculcations of Christianity, which lays upon hu- 
man nature its broad and eternal requirement, ' to do good.' From 



XVI rNTEODUCTIOW. 

tliis authoritative iiioral demand science cannot be exempted. The 
power it confers is to be held and used as power is exercised by God 
himself, for purposes of universal blessing. 

"We place a high estimate upon the advantages which society may 
reap from a better acquaintance with material phenomena, for life is a 
stern realm of cause and effect, fact and law. To the poetic day-dreamer 
it may be an affair of sentiment, an ' illusion,' or a ' vapor,' but to 
the mass of mankind, life is a solid, unmistakable reality, that will not 
dissolve into mist and cannot be conjured out of its qualities. As such, 
we would deal with it in education, giving prominence to those forms 
of knowledge which will work the largest practical alleviations and 
most substantial improvement throughout the community. But it is 
wisely designed that those studies which may become in the highest 
degree useful are also first in intellectual interest. It is a grievous mis- 
take to suppose that the study of natural science martyrizes the more 
ethereal faculties of the soul, and dooms the rest to painful toil among 
the naked sterilities of commonplace existence. So far from being un- 
friendly to the imagination, as is sometimes intimated, science is its 
noblest precursor and ally. Can that be unfavorable to this faculty, 
which infinitely multiplies its materials, and boundlessly amplifies its 
scope ? Can that be restrictive of mental sweep, which unlocks the 
mysteries of the universe and pioneers its way far into the councils of 
Omniscience ? Who was it that lifted the veil, and disclosed a new 
world of exquisite order and beauty in all the commonest and vulgar- 
est forms of matter, below the former reach of eye or thought ? Who 
was it that dissipated the fabulous 'firmament,' which primeval igno- 
rance had mounted over its central and stationary earth ; set the world 
in motion, and unfolded a plan of the heavens, so appalling in ampli- 
tude that imagination itself falters in the survey ? Who was it that 
first read the handwriting of God upon the rocks, revealing the history of 
our planet and its inhabitants through durations of which the mind had 
never befoi-e even presumed to dream ? In thus unsealing the mysteries 
of being — in turning the commonest spot into a museum of wonders — 
who can doubt that science has opened a new and splendid career for 
the play of the diviner faculties ; and that its pursuit affords the most 
exhilarating, as well as the healthiest and purest of intellectual enjoy- 
ments? Nor should we forget its elevating tendencies; for in con- 
templating the varied scheme of being around, its beauties, harmonies, 
adaptations, and purposes of profoundest wisdom, the thoughts ascend 
in unspeakable admiration to the infinite Source of truth and light. 
We should educate and elevate our nature by these studies, storing our 



INTRODUCTION. XVU 

minds with the richest materials of thought, enlarging our capacities 
of benign exertion, and rising to a more intimate communiou Avith the 
spirit of the Great Maker of all. 

But beyond these considerations, physical science has another claim 
upon the Instructor, in the kind and extent of the mental discipline it 
affords. The study of mathematics has a conceded value in this rela- 
tion, being eminently favorable to precision and persistence of the 
mental operations — to steadfast concentration of thought upon ab- 
stract and difficult subjects. But we hope not to incur the charge of 
educational heresy,by expressing the opinion,that its training is some- 
what defective — is neither sufficiently comprehensive, nor altogether 
of the right kind. Its influence is limited to certain faculties only, and 
the metJiod to which it accustoms the mind is too little available in 
grappling with the practical problems of life. The starting-point of 
the mathematician is certain universal truths of consciousness, intui- 
tive axioms — assumed without proof, because they are self-evident, and 
thei-efore incapable of proof. From these, by various operations and 
chains of reasoning, he proceeds to work out special applications. His 
direction is from generals to particulars — it is inferential — deductke. 
But when we come to deal with the phenomena of the external 
world, and the actualities of daily experience, this plan fails, and we 
are driven to the very reverse method. In the phenomenal world we 
are without the eternal principles, settled and assumed at the outset ; 
these become themselves the objects of investigation ; they have to be 
established, and we must begin with particulars, special inquiries, 
experimental investigations, the observation of facts, and from these 
we cautiously proceed to general truths — to universal principles. 
The process is an ascent from particulars — generalization — induc- 
tion. That the whele is greater than a part, or that two parallel lines 
will never intersect each other, are irresistible intuitions, taken for 
granted at once by all minds. But that matter attracts matter with 
a force proportional to the square of its distance ; or that chemical 
combination takes place in definite unalterable proportions, are truths 
oi induction — general laws, only arrived at after long and laborious in- 
vestigation of particular facts. These are essentially opposite methods 
of proceeding in different departments of inquiry, each correct in its 
own sphere, but false out of it. The human mind started with the 
mathematical method, and the greatest obsti'uction to the progress of 
physical science for many centuries arose from the attempt to apply 
it to outward phenomena ; that is, to assume certain principles as true 
of the external world, and to reason from them down to the facts; m* 



XVIU INTRODUCTION 

stead of beginning with the facts, and carefully evolving the general 
laws. The splendid achievements of modern science are the fruit of 
the inductive method. This should be largely joined with the mathe- 
matical to secure a full and harmonious mental discipline. It edu- 
cates the attention by establishing habits of accurate observation, 
strengthens the judgment, teaches the supremacy of facts, cultivates 
order in their classification, and develops the reason through the es- 
tablishment of general principles. It is claimed, as an advantage of 
mathematics, that it deals with certainties, and, raising the mind above 
the confusions and insecurities of imperfect knowledge, habituates it 
to the demand of absolute truth. That benefits re ay arise from this 
exalted state of intellectual requirement, we are far from doubting, 
and are conscious of the danger of resting satisfied with any thing 
short of perfect certitude, where that can be attained. But here 
again there is possibility of error. Mathematical standards and pro- 
cesses are totally inapplicable in the thousand-fold contingencies of 
common experience ; and the mind which is deeply imbued with its 
spirit, is little attracted to those departments of thought, where, after 
the utmost labor, there still remain doubt, dimness, uncertainty and 
entanglement. And yet, sueh is precisely the practical field in which 
our minds must daily work. The mental discipline we need, there- 
fore, is not merely a narrow deductive training of the faculties of cal- 
culation, with their inflexible demand for exactitudes ; but such a sys- 
tematic and symmetric exercise of its several powers as shall render 
it pliant and adaptive, and train it in that class of intellectual opera- 
tions which shaU best prepare it for varied and serviceable intellec- 
tual duty in the practical aflairs of life. 

There is still another thought in this connection which it is im- 
portant should be expressed. It has been too much the policy of the 
past so to train the mind as to enslave, rather than to arouse it. Edu- 
cation, from the earliest time, has been under the patronage of civil 
and ecclesiastical despotisms, whose necessary policy has becyi tlie re- 
pression of free thought. The state of mind for ever insisted on has 
been that of submissive acceptance of authority. Instead of laying 
open the limitations, uncertainties, and conflicts of knowledge, which 
arise from its progressive nature, the sj)irit of tlie general teaching 
has been that all things are settled, and that wisdom has reached its 
last fulfilment. Instead of encouraging bold inquiry, and inciting to 
noble conquest, the effect has rather been to reduce the student to a 
mere tame, unquestioning recipient of established formulas and 
time-honored dogmas. It is obvious on all sides that this state 



INTRODUCTION. ' XIX 

of things has been deeply disturbed. The introduction of Re- 
publicanism, with political freedom of speech and action; the 
advent of Protestantism, with religious liberty of thought; and 
the splendid march of science, which has enlarged the circle 
of knowledge, multiplied the elements of power, and scattered social 
and industrial revolution, right and left, for the last hundred years — 
these new dispensations have invaded the old repose, and fired the 
minds of multitudes with a new consciousness of power. Yet we 
cannot forget that our education still retains much of its ancient 
spirit, is yet largely scholastic and arbitrarily authoritative. We 
believe that this evil may be, to a considerable degree, corrected 
by a frank admission of the incompleteness of much of our knowl- 
edge; by showing that it is necessarily imperfect, and that the 
only just and honest course often involves reservation of opinion 
and suspension of judgment. This may be consonant neither with 
the teacher's pride nor the pupil's ambition, nevertheless it is 
imperatively demanded. "We need to acquire more humility of 
mind and a sincerer reverence for truth ; to understand that much 
which passes for knowledge is unsettled, and that we should be 
constant learners through life. The active influences of society, 
as well as the school-room, teach for other lessons. We are com- 
mitted in early childhood to blind partisanships, — political and 
religious, — and drive on through life in the unquestioning and unscru- 
pulous advocacy of doctrines which are quite as likely to be false as 
true, and are perhaps utterly incapable of honest definitive adjustment. 
Science inculcates a difierent spirit, which is most forcibly illustrated 
in those branches where absolute certainty of conclusion is difficult of 
attainment. Mr. Paget has urged the salutary infiuence of the study 
of physiology in this relation. He says, " It is a great hindrance to the 
progress of truth, that some men will hold with equal tenacity things 
that are, and things that are not, proved ; and even things that, from 
their very nature, do not admit of proof. They seem to think (and 
ordinary education might be pleaded as justifying the thought) that a 
plain ' yes ' or ' no ' can be answered to every question that can bo 
plainly asked ; and that every thing thus answered is to be maintained 
as a point of conscience. I need not adduce instances of this error, 
while its mischiefs are manifested every where in the wrongs done by 
premature and tenacious judgments. I am aware that these are faults 
of the temper, not less than of the judgment ; but we know how much 
the temper is influenced by the character of our studies ; and I think 
if any one were to be free from this over-zeal of opinion, it should bo 



XX INTKODUCnON. 

one who is early instructed in an uncertain science such as physiology.' 
In the present work, the chief statements comprised under heat, light, 
and air, may be regarded as settled with a high degree of certainty, 
while much of the matter relating to food and its effects is less clearly 
determined ; — its truth is only approximative, and we have stated it, 
as such, without hesitation. While the reader is informed, he is at 
the same time apprised of the incompleteness of hig knowledge. 

An important result of the more earnest and general pursuit of 
science, by the young, will be, to find out and develop a larger number 
of minds having natural aptitudes for research and investigation. As 
there are born poets, and born musicians, so also there are born in- 
ventors and experimenters ; minds originally fitted to combine and 
mould the plastic materials of nature into numberless forms of useful- 
ness and value. It is a vulgar error that the work of discovery and 
improvement is already mainly accomplished. The thoughtful well 
understand that man has hardly yet entered upon that magnificent 
career of conquest, in the peaceful domain of nature, to which he ia 
destined, and which will be hastened by nothing so much as a more 
general kindling of the minds of the young with enthusiasm for science. 
The harvest awaits the reapers — how strange that man should have 
neglected it so long. Fuel, air, water, and the metals, as we see them 
acting together, now, in the living, laboring steaiii-eugine, have been 
waiting from the foundation of the world for a cliance to relieve man 
of the Avorst drudgeries of toil. Long and fruitlessly did the sunbeam 
court the opportunity of leaving upon the earth permanent impressions 
of the things he revealed ; while the lightning, though seemingly a 
lawless and rollicking spirit of the skies, was yet impatient to bo 
pressed into the quiet and useful service of man. Can there be a 
doubt that other powers and forces, equally potent and marvellous, 
await the discipline of human genius ? Not in vain was man called 
upon, at the very morning of creation, to 'subdue the earth.' Already 
has he justified the bestowment of the viceroyal honor : who shall 
speak of the possibilities that are waiting for him in the future ! 



o. 



THE 

HAND-BOOK OF HOUSEHOLD SCIENCE. 



PART FIRST. 
HEAT. 



I. SOURCES AND DISTRIBUTION OF TERRESTRIAL HEAT. 

1. Nature of onr Knowledge concerning Heat. — When we place tlio 

hand ui^on a stove with a fire in it, a feeling of warmth is experienced, 
while if it he made to touch ice, there is a sensation of cold. The im- 
pressions are supposed to he caused in hoth cases hy the same force or 
agent ; in the first instance, the impulse passing from the heated iron to 
the hand ; in the second, from the hand to the ice. What the nature 
or essence of this thing is, which produces such different feelings hy 
moving in opposite directions, and which makes the difference be- 
tween summer and winter, nobody has yet discovered. It is named 
heat. Some have conjectured it to be a kind of material fluid, exceed- 
ingly subtle and etliereal, having no weight, existing diffused through- 
out all things, and capable of combining with every known species of 
matter; and this supposed fluid has received the name of caloric. 
Others think heat is not a material thing, but merely motion: either 
waves, or undulations produced in a universal ether, or a very rapid 
vibration, or trembling of the particles of common matter, which is in 
some way contagious, and passes from object to object. Of the essen- 
tial nature of heat we understand nothing, and are acquainted only 
with its effects: — our information is limited to its behavior. It resides 
in matter, moves through it, and is capable of variously changing its 
conditions. It is an agent pi'oducing the most wonderful results every 
where around and even within us ; — a force of such tremendous energy, 
such far-reaching, all-pervading influence, — that we may almost venture 
to say it has been appointed to take control of the material universe ; 



18 SOURCES OF TEERESTEIAL HEAT. 

while in the plan of the Creator, it is so disciplined to the eternal re« 
straints of law, as to become the gentle minister of universal benefi- 
cence. 

2. To what Extent the Earth is warmed by the Son. Heat comes 
from the sun to the earth in streams or rays associated with light. It 
has been ascertained by careful measurement, that the quantity of 
solar heat which falls upon a square foot of the earth's surface in a 
year would be sufficient to melt 5400 lbs. weight of ice ; and as a 
cubic foot of ice weighs 54 lbs., the heat thus annually received would 
melt a column of it 100 feet high, or a shell of ice enveloping our 
globe 100 feet thick. As the sun turns around once in 25 days, thus 
constantly exposing different parts, we conclude that equal quantities 
of heat are thrown from all portions of his surface, and are thus ena- 
bled to calculate the total amount of heat which he imparts annually. 
K there were a sphere of ice 100 feet in thickness completely sur- 
rounding the sun, at the same distance from him as the earth's orbit, 
his heat would be sufficient to melt it in the course of a year. This 
quantity of heat would melt a shell of ice enveloping the sun's surface 
38.6 feet thick in a minute, or 10.5 miles in thickness in a year. "We 
are, therefore, warmed by heat-rays shot through a hundred million 
miles of space, from a vast self-revolving grate having fifteen hundred 
thousand miles of fire-surface heated seven times hotter than our 
fiercest blast furnaces. 

8. We get Heat also from the Stars. — Although the sun is the most 
obvious and conspicuous source of heat for the earth it is by no means 
its sole source. Of the enormous quantity of heat that streams away 
in aU directions from his surface, the earth receives but a small frac- 
tion. But it is neither lost nor wasted ; he not only warms the earth, 
but assists to warm the universe. Our globe catches a trifling portion 
of his rays ; but the rest fly onward to distant regions, where all are 
finally intercepted by the wandering host of orbs with which the 
heavens are fiUed. And what the sun does, all the other stars and 
planets are also doing. A mighty system of exchanges (32)* is estab- 
lished among the bodies of space, by which each radiates heat to all 
the rest, and receives it in turn from all the rest, according to the 
measure of its endowments. The whole steUar universe thus contrib- 
utes to our warmth. It is a startling fact, that if the earth were de- 
pendent alone upon the sun for heat, it would not get enough to make 
the existence of animal and vegetable life possible upon its surface. 

* These numbers refer to paragraphs. « 



ITS UNEQUAi. DISTKIBUTION, 19 

It results from the researches of Pouillet, that the starry spaces fur- 
nish heat enough in the course of a year to melt a crust of ice upon 
the earth 85 feet thick, almost as much as is supplied hy the sun. 
This may appear strange, when we consider how immeasurahly small 
must be the amount of heat received from any one of these distant 
bodies. But the surprise vanishes, when we remember that the whole 
firmament of heaven is so thickly sown with stars, that in some places 
thousands are crowded together within a space no greater than that 
occupied by the full moon. (Dr. Lardnee.) 

4. Heat aii£qaally Distributed upon the Eartb. — The quantity of heat 
which the earth receives from the sun is very unequal at different 
times and places. The earth turns around every day; it is globular 
in form, and is constantly changing the position of its surface in rela- 
tion to the sun, as it travels about him in its annual circuit. The con- 
sequence is, that we receive more heat during the day than at night ; 
more at the equator than toward the poles ; more in summer than in win- 
ter. "We are all aware that the temperature may fall from blood heat 
at mid-day, to the point of frost or freezing at night ; and while at the 
equator they have a temperature averaging, the year round, 81-5 
degrees, at New York (less than 3,000 miles north), the average annual 
heat falls to 50 degrees ; and at Labrador (less than a thousand miles 
further north), the average temperature of the year sinks below freez- 
ing. Nor do places at the same distance from the equator receive 
equal amounts of solar heat. A great number of circumstances 
connected with the surface of the earth, disturb its regular and uniform 
distribution. Dublin for example, though between eight and nine 
hundred miles further from the equator than New York, has as high 
a yearly temperature. Some places also experience greater contrasts 
than others between the different seasons: thus while New York 
has the summer of Rome, it has also the winter of Copenhagen. 

II.— INTLUENCE OF HEAT UPON THE LIVING WORLD. 

5. It Controls the Distribution of Vegetable Life. — It is this variable 
quantity of heat received at different places and seasons, which deter- 
mines the distribution of life upon the globe. Certain tribes of plants, 
for example, flourish in the hot regions of the tropics, and cannot live 
with a dimmished intensity of heat. Accordingly, as we pass to the 
cooler latitudes, they disappear, and new varieties adapted to the new 
conditions take their place. As we pass into still colder regions, these 
again give way to others of a hardier nature, or which are capable of 



20 INTLUENCE OF HEAT UPON THE LIVING WOELD, 

living where there is less heat. As we proceed from the hot equator 
to the frozen poles, or as we pass upward from the Avarm vaUey to the 
snowy summit of a lofty mountain, we cross successive belts of varying 
vegetation, which are, as it were, definitely marked off by the different 
quantities of heat which they receive. " In the tropics wo see the 
palms, which give so striking a characteristic to the forests, the broad- 
leaved bananas, and the great climbing plants, which throw them- 
selves from stem to stem, like the rigging of a ship. Next foUows a 
zone described as that of evergreen woods, in which the orange and 
the citron come to perfection. Beyond this, another of deciduous 
trees — the oak, the chestnut, and the fruit trees with whicli, in this 
climate, we are so well acquainted ; and here the great climbers of 
the tropics are replaced by the hop and the ivy. Still further advanc- 
ing, we pass tln-ough a belt of conifers — firs, larches, pines, and other 
needle-leaved trees — and these, leading through a range of birches, 
which become more and more stunted, introduce us to a region of 
mosses and saxifrages, but which at length has neither tree nor shrub ; 
and finally, as the perpetual polar ices are reached, the red snow algae 
is the last trace of vegetable organization." 

6. Heat Regulates the Distribation of Animals. — It is the same also 
with animal life. Different animated races are adapted to different 
degrees of temperature, and belong within certain heat-limits, just like 
plants. In going from the equator to the poles, different classes of 
animals appear and fade away, as the temperature progressively de- 
clines. Some are adapted to the alternations of winter and summer 
by changes of their clothing ; and others, as birds, are pursued from 
region to region by the advancing temperatui-es. Animals whose con- 
stitutions are conformed to one condition of heat, if transported to 
another, suffer and perish: whUe the lion is confined to his torrid 
desert \^i sand, the polar bear is imprisoned in the frigid desert of ice ; 
and, in both cases, the sunbeam is the chain by which they are bound. 

7. Heat Inflnences Man's Physical Development. — l^or does man fur- 
nish an exception to these controlling effects of temperature. The 
striking peculiarities of physical appearance and endowment, exliibited 
by different tribes and communities of men, is well known ; and it has 
long been understood that much of these differences is due to the all- 
powerful influence of heat. " The intense cold, dwarfs and deforms the 
inhabitant of the polar regions. Stunted, squat, large-headed, fish- 
featured, short-limbed and stiff-jointed, he resembles in many points 
the wolves and bears in whose skins he wraps himself. As he ap- 
proaches the sunny south, his stature expands, his limbs acquire shape 



W AFFECTS MIND AND CHAJEACTER. 21 

and proportiou, and his features are ameliorated. In the genial region, 
he is beheld with that perfect conformation, that freedom of action 
and intellectual expression, in which grace and beauty consist." 

8. Extremes of Dress in Differeat Localities. — The remarkable contrasts 
of temperature which different races experience, is well illustrated by 
t.lieir circumstances of dress. "While in the West Indian Islands a 
single fold of cotton is often found to be an incumbrance, the Green- 
lander wraps himself in layer after layer of woollens and furs, fox-skins, 
sheep-skins, wolf-skins, and bear-skins, until we might suppose him 
well guarded against the cold ; yet with a temperature often a hundred 
degrees below the freezing-point, he cannot always protect himself 
against frozen extremities. Dr. Kajste observes, " rightly clad, he is a 
lump of deformity waddling over the ice: unpicturesque, uncouth, 
and seemingly helpless. It is only when you meet him covered with 
frost, his face peering from an icy halo, his beard glued with frozen 
respiration, that you look with intelligent appreciation on his many- 
coated panoply against king Death." 

9. Temperature and Character. — The effect of cold is to benumb the 
body and blunt the sensibility ; while warmth opens the avenues ot 
sensation, and increases the susceptibility to external impressions. 
Thus, the intensity with which the outward world acts upon the inward 
through the sensory channels, is regulated by temperature. In cold 
countries the passions are torpid and sluggish, and man is plodding, 
austere, stolid, and unfeeling. "With the barrenness of the earth, there 
is sterility of thought, poverty of invention, and coldness of fimcy. 
On the other hand, the inhabitants of torrid regions possess feverish 
sensibilities. They are indolent and effeminate, yet capable of furious 
action ; capricious in taste, often ingenious in device ; they are extrav- 
agant and wild in imagination, delighting in the gorgeous, the daz- 
zling, and the marvellous. In the medium heat of temperate climates, 
these marked excesses of character disappear; there is moderation 
without stupidity, and active enterprise without fierce impetuosity. 
Society has more freedom and justice, and the individual more con- 
stancy and principle : with loftiness of thought, there is also chastening 
of the imagination. By comparing the effects of climate in the tor- 
rid, temperate, and frigid zone, we observe the determining influenco 
of external conditions, not only upon the physical nature of man, but 
over the mind itself. ""We may appeal to individual experience for 
the enervating effects of hot climates, or to the common understanding 
of men as to the great control which atmospheric changes exercise, 
not only over the intellectual powers, but even on our bodily well- 



22 INPLUENCE OF HEAT UPON THE LIVING WORLD. 

being. It is "within a narrow range of climate that great men have 
been born. In the earth's southern hemisphere, as yet, not one has 
appeared ; and in the northern, they come only within certain paral- 
lels of latitude. I am not speaking of that class of men, who in all 
ages and in every country, have risen to an ephemeral elevation, and 
have sunk again into their native insignificance so soon as the causes 
which have forced them from obscurity cease, but of that other class 
of whom God makes but one in a century, and gives him a power of 
enchantment over his fellows, so that by a word, or even by a look, 
he can electrify, and guide, and govern mankind." — (Dr. Deapee.) 

10. Influence of the Supply of Fuel. — The abundance or scarcity of the 
supply of fuel, as it controls the amount of artificial heat, exerts a power- 
ful influence upon the condition of the people in various ways ; indeed, 
it may involve the health and personal comfort of whole nations, to 
such an extent, as even to contribute to the formation of national char- 
acter. "Where fuel is scarce, houses are small, and their occupants 
crowded together ; the external air is as much as possible excluded ; 
the body becomes dwarfed ; and the intellect dull. The diminutive 
Laplander spends his long and dreary winter in a hut heated by a 
smoky lamp of putrid oil ; an arrangement which afflicts the whole 
nation with blear eyes. Scarcity of fuel has not been without its 
effect in forming the manners of the polished Parisians, by transfer- 
ring to the theatre and the cafe those attractions, which, in countries 
where fuel is common and cheap, belong essentially to the domestic 
hearth. 

11. Temperature and Language. — Aebtjthnot suggested not only that 
heat and air fashion both body and mind, but that they also have a 
great effect in forming language. He thought the serrated, close 
way of speaking among the northern nations, was owing to their 
reluctance to open their mouths wide in cold air, which made their 
speech abound in consonants. From a contrary cause, the inhabitants 
of warm climates formed a softer language, and one abounding in 
vowels. The Greeks, inhaling air of a happy medium, were celebrated 
for speaking with the wide-open mouth and a sweet-toned, sonorous 
elocution, 

12. Man may Make his own Climate. — So controlling is this agent, 
and yet man comes into the world defenceless from its invasions; 
provided with no natural means of protection from its disturbing and 
destructive influence. But in the exercise of that intelligence which 
gives him command over nature, he has studied the laws, properties, 
and effects of heat, and the methods by which it may be produced 



IT INFLUENCES THE DIMENSIONS OE BODIES. 23 

and regulated. He has devised the means of creating an artificial and 
portable climate, and thus of releasing himself, in a great measure, 
fi-om the vicissitudes of temperature. We are to regard the production 
and control of artificial climate, as an art involving the development 
and expansion of mind and body, the preservation of health and the 
prolongation of life. Such has been the thought expended upon this 
subject, and so important the results to the well-being of man, that we 
may almost venture to measure the civilization of a people, by the per- 
fection of its plans and contrivances for the management of heat. 

III.— MEASUREMENT OF HEAT. THE THERMOMETER. 

13. Heat tends to Equal Diffasion. — We have said that heat is a force, 
or energy, existing everywhere throughout nature. Every kind of 
matter which we know contains heat, but all objects do not contain 
equal quantities of it. If left to follow its own law, heat would dis- 
tribute itself through aU the matter around, until each body received 
a certain share ; and it would then be in a condition of general rest, or 
equal balance, (equilibrium.) It is to this state that heat constantly 
tends. If a very hot body of any kind is brought into a room, we all 
know it will at once begin to lose its heat, and that the temperature 
contkiues to descend until it is the same as the surrounding air, walls, 
and furniture. 

14. How do we get acquainted with Heat?— But before heat can 
tend to equilibrium, it must first be thrown out of this state. There 
are forces which tend to disturb the equal balance of heat, causing it 
to leave some bodies, and accumulate in others in unusual or excessive 
quantities. It is the passing of heat from body to body, from place to 
place, — robbing one substance of it and storing it up in another ; in 
short, its motion, and the effects it produces, which enable us to 
become acquainted with it. How, then, may we know when one. sub- 
stance has been deprived of heat and another has received it ? or how 
can we ascertain the quantity of it which a body possesses ? 

15. Heat accnmnlating In Bodies, enlarges them.— It is an effect of 
heat, that when it enters into bodies it makes them larger ; it increases 
their bulk, or expands them, so that they occupy more space than they 
did before. A measure that will hold exactly a gallon in winter, will 
be expanded by the heat of summer so as to hold more than a gallon. 
The heat of summer lengthens the foot-rule and yard-stick. A pen- 
dulum is longer in summer than in winter, and therefore swings or 
vibrates slower, which causes the clock to lose time. Twenty-three 



24 MEASUREMENT OF HEAT. 

pints of water, taken at the freezing point, would expand into twenty- 
four by being heated to boihng. The difference in the heat of the 
seasons affects sensibly the bulk of liquors. In the height of summer, 
Fio. 1. spirits will measure five per cent, more than in the 

depth of winter. (Geaham.) "When 180 degrees of 
heat are added to iron, 1000 cubic inches become 
1045 ; 1000 cubic inches of air become 1365. Some 
substances, however, in solidifying expand. This is 
the case with watei", which attains its greatest 
density, or shrinks into its smallest space, at the 
temperature of 38"8°, as seen in fig. 1. From this 

.,.,11 . ^ , point, either upward or downward, it enlarges: and 

iJ«,8h point of ^ - ' '^ „ ' \ 

32'] \ greatest at freezmg, or 32 , the expansion amounts to about 

ensi y. ^^-j^ ^^ .^^ bulk. Ice therefore floats upon the surface 

of water. The wisdom of this exception is seen, 

when we reflect, that if it sank as fast as it is formed, 

whole bodies of water would be changed to solid ice. 

16. Relatiou between Heat and Expansion. — In the same manner, all 
the objects about us are changed in their dimensions as heat enters or 
leaves them. Different substances expand difterently by the same 
quantities of heat ; but when a certain measured amount is added to, or 
taken from the same kind of substance, it always swells or shrinks to 
exactly the same extent. The variation of size produced in solid sub- 
stances, such as wood, stone, or iron, is very small ; we should not be 
aware of it without careful measurement. The same proportion of 
heat causes liquids, such as water, alcohol, and mercury, to vary in 
bulk more than solids ; while heat added to gases, or airs, produces a 
much greater expansion than it does in liquids. Although heat thus 
causes bodies to occupy more space and become larger, yet it does not 
make them heavier. The same substance weighs exactly the same, no 
matter how cold or how hot it is ; hence heat is called imponderable. 

17. Principle and Construction of the Thermometer. — If, then, when 
a substance receives a certain quantity of heat, it undergoes a certain 
amount of enlargement, we can use that enlargement as a measure of 
the heat ; and this is what is done by the thermometer or heat-meas- 
nrer. A common thermometer is a small glass tube, with a fine 
aperture or hole through it, like that in a pipe stem, and a hollow 
bulb on one end of it fig. 2. This bulb and part of the tube is filled 
with the liquid metal mercury. By suitable means, the air is removed 
from the empty part of the tube, and its open end sealed up. The 
bulb is then dipped into water containing ice, and a mark is made 



SCAXES OF TUERMOMETERS. 



25 



Scale. 

212° 



182° 



CentiCTade 
Scale. 



Zero. 



apon the tube at the top of the mercurial column. This pcint of 
melting ice is the same as that at which water freezes, and is hence 
caUed i\iQ freezing point. The tube is then Fig. 2. 

removed, and dipped into boiling water. Fahrenheit's 
The heat passes from the water, through 
the glass, into the mercury, which rapidly 
expands and rises through the narrow 
bore. It passes up a considerable distance, 
and then stops ; that amount of heat will 
expand it no more. The height of the 
mercury is again marked upon the tube, 
and this is called the 'boiling point of water. 
The distance upon the tube between these 
two points is then marked off into 180 
spaces, which are called degrees, and 
marked (°). Now, it is clear that the 
amount of heat whicli runs the mercury 
up through these 180 spaces is precisely 
the same quantity that changed the water 
from the freezing to the boiling point ; so 
that we may say that the water in this 
case received 180 degrees of heat. If we 
mix a pound of water at the boiling point with another pound at the 
freezing point, the result will be a medium ; and if the thermometer 
is plunged into it, the mercury will stand at the ninetieth space — that 
is, it contains 90 degrees of heat according to this scale of meas- 
urement. And so, by dipping the thermometer into any vessel of 
water, we ascertain how much heat it contains. 

18. How Thermometers are Graduated or Marked. — But this is not 
the way that the scale of the common thermometer is actually marked. 
Its inventor, Faheenhkit, instead of beginning to count his degrees 
upward from the freezing point, thought it would be better to begin 
to count from a point of the extremest cold. Accordingly, he mixed 
salt and snow (55) together, and putting his thermometer in it, the 
mercury fell quite a distance lower than the freezing point of water. 
This he supposed to be the greatest cold it is possible to get, though 
an intensity of cold has since been obtained 150° lower. Marking 
off this new distance through which the mercury had fallen, in the 
same way as above, he got 32 additional spaces or degrees. Calling 
this point of least heat or greatest cold he could get, nought or zero 
be counted up to the freezing point of water, which was 32°, and 
2 



Thermometer. 



26 MEASUREMENT OP HEAT. 

adding this to the 180 above, he got 212 as the boiling point of water. 
This is the way we find the common thermometer scale marked (Fig. 
2) lapon brass plates, to which the glass tube is attached. The centi- 
grade thermometer calls the point of melting ice zero, and marks the 
space up to boihng water into 100 degrees. In Reaumur's thermometer, 
the same space is divided into 80 degrees. Degrees below zero aro 
marked with the minus sign, thus — . It deserves to be remarked, 
that the glass tube expands by heat as well as the mercury, but by no 
means to so great a degree. And besides, there being a considerable 
quantity of mercury in the bulb, it requires but a very small expansion 
of it to push the quicksilver up the narrow tube, through a perceptible 
space. 

19. Exactly what the Thermometer iudicatesi — The word thermometer 
is derived from thermo, heat, and metron^ measure, and it therefore 
signifies heat-measurer. But what does it measure ? That which is 
measured we usually name quantity. But we must not suppose that 
the thermometer indicates quantities of heat in any absolute sense. 
For example, if we dip a gill of water from a spring va. one vessel, 
and a gallon in another vessel, a thermometer wiU indicate exactly 
the same degree of heat in one as in the other ; but we cannot thence 
infer that the absolute quantity of heat is as great in the giU of water 
as in the gallon. The thermometer shows us simply the degree of in- 
tensity of the heat in its mercury ; and as this constantly tends to the 
same point as that of surrounding bodies, we take its degree to bo 
their degree. If the thermometer suspended in a room stands at 70°, 
we say the room is at 70°, because heat tends to equalization. 
If by opening windows or doors the thermometer falls to 60°, we say 
the room has lost 10° of heat, — speaking of it as a measured quantity. 
The instrument indicates variable degrees of intensity, which are con- 
verted into expressions of quantity. We shall shortly see that there 
are certain conditions of heat which the thermometer totally faUs to 
recognize. 

20. Importance of the Domestic use of the Thermometer. — As the ques 
tion of temperature is one of daily and hourly interest, not only of 
the utmost importance in conducting numerous household operations, 
but of the highest moment in relation to the maintenance of health, 
it will at once be seen that a thermometer is indispensable. Every 
family should have one, and accustom themselves to rely upon it as a 
practical guide in relation to heat, and not to depend upon feeling or 
guessing. Thermometers costing from fifty cents to a dollar and a half, 
will answer all ordinary purposes. They are so mounted that the scale 



THEKMOMETEES AUD THEIR INDICATIONS. 27 

and tube may be drawn out of the frame, so that the bulb can be im- 
mersed in a liquid, if required. They must be gradually warmed before 
dipping in hot liquids to prevent fracture of the glass, and of course 
need to be handled with much care. Their scales extend no higher 
than the boiling point of water. There is usually some departure from 
the accurate standard in the indications of the cheaper class of instru- 
ments. Mr. Tagliabue, a prominent maker of this city, states that these 
variations rarely exceed from 1 to 2 degrees. 

21. Interesting Facts of Temperature. — We group together a few 
points of temperature of famUiar interest.* 

Best temperature for a room 65°-68* 

Lowest temperature of human body (in Asiatic cliolera) 67* 

Mean temperature at the equator 81* 

Heat of the blood 98* 

Beef s tallow melts 100* 

Mutton tallow melts 106* 

Highest temperature of human body (in tetanus or lockjaw) .... 110* 

BtearLne melts Ill* 

Spermaceti melts 112* 

Temperature of hot bath 110°-180* 

Phosphorus inflames. Friction matches ignite 120* 

Tea and coffee usually drank . . ISO'-l'W 

Butter melts 130°-140* 

Coagulation of albumen 145* 

Scalding heat . . , • . . . 150* 

Wax melts 155° 

MilkboDs • . . . . 199* 

Sulphur melts 226° 

Cane sugar meltu 820° 

Baking temperature of the oven 820°-400* 

Sulphur ignites 660* 

Heat of the common fire 1000' 



IV. KADIATION OF EEAT AND ITS EFFECTS. 

22. Heat passing through Bodies. — Heat in motion around us is con- 
stantly passing through some substance, or from one material body to 
another. But aU substances do not behave alike toward it. They do 
not aU receive, retain, or part with it in the same way. Through cer- 
tain bodies it passes rapidly in straight lines, like rays of light, and is 
then termed radiant heat, and this kind of heat-motion is called radi- 
ation^ and the substances which allow it to pass through them are said 
to transmit it. We receive radiant heat from the sun and from arti- 
ficial fires ; and the air is one of those substances which permit it to 
pass through. 

* For a further list of tcmperaldrcs. see Appendix, A. 



28 



RADIATION AND ITS EFFECTS. 



X-^' 



Eadiation of heat. 



23. Decrease iu the Force of Heat-rays. — When heat radiates from 
any source, as the sun, a stove, an open fire, or flame, it passes from 
each point in all directions Fig. 3 ; it spreads out or diverges as it 
Fig. 8. passes away so as to become weaker and much 

/ less intense. It decreases in power at a regular 

/ / ,-' numerical rate, as seen in Fig. 4. It is commonly 

f/,y,''',,' said that the intensity of radiant heat decreases 
inversely as the square of the distance ; that is, 
if in standing before the fire at a distance of two 
feet from it, we receive a certain amount of 
heat, and tJien we step back to twice that dis- 
tance, we shall receive but one fourth the quan- 
tity ; at thrice the distance, but one ninth ; and 
at four times the distance, but one sixteenth the 
quantity, as is shown in Fig. 4. But this state- 
ment is only true when we consider the heat as passing from a single 
point. When it flows from an infinite number of adjacent points, — that 
Fig. 4. is, a surface^ which is the way 

it is practically emitted, it does 
not decrease at so rapid a rate. 
24. Diflferent kinds of Heat.— 
We all know that some substan- 
ces will let light pass through 
them, and others will stop it. 
It is just so with heat : but the 
same substances which transmit 
light, do not always transmit 
heat. Air allows both to pass 
Showing the rate at which radiant heat is without obstruction ; but water, 
diffused and weakened. ^j^j^^ ^^ ^^.g^jy ^X^osss, the pas- 

sage of light, has very little power to transmit heat. Rays of light, 
passing through water, are strained of nearly all their heat. But 
there seems to be a difference in the source and nature of the heat 
itself, as to its power of getting through various bodies. Glass allows 
solar heat to go through it, but not artificial heat. A pane of glass 
held between the sun and one's face will not protect it from the 
Keat ; but it may be used as a fire-screen. If we place a plate of 
j,dass and of rock-salt before a hot stove, the dark heat will pass 
treoly through the salt, but not through the glass. The glass is, 
therefore, opaque to heat (if wo may borrow the language of light), 
while salt is transpoA-ent to it, and is hence called the glass of heat. 




CIKCtTMSTANCES CONTROLLING IT. 29 

Mbloni has shown that if tlie quantity of dark, radiant lieat transmit- 
ted through air, he expressed hy 100, the quantity transmitted through 
an equal thickness of a plate of rock-salt will he 92; flint glass, 67; 
crown glass, 49 ; alum, 12 ; water, 11. 

25. Heat which docs not go through is Absorbed. — When a substance 
does not permit all the rays of heat which strike upon it, to pass 
through, those which are detained, or lodged within it, are said to he 
adsorbed by it. Thus, fine window-glass transmits only 49 heat rays in 
a liundred, the remaining 51 being absorbed by it. Now it is clear, 
that if all the heat pass through a substance, none can accumulate in 
it to warm or heat it. It is the heat detained or lodged in a body that 
warms it. The heating power is proportional to absoi-ption. The 
atmosphere lets the sun's heat all pass — does not absorb it ; it is there- 
fore not wai'med by it. 

26. Conditioas of Radiation. — The power of a body to emit or radiate 
heat, depends first, upon the quantity which it contains. Other things 
being the same, tlie higher its temperature compared Avith the sur- 
rounding medium, the more rapidly will it throw oft' its heat. As it 
cools, the radiation becomes slower and slower. But all subtances at 
the same temperature, do not throw out their heat alike. The condi- 
tion of surfaces exerts a powerful control over radiation. Rough, 
uneven surfaces radiate freely, while smooth, polished surfaces offer a 
barrier to heat, which greatly hinders its escape. Metals, as their sur- 
faces are capable of the highest polish, are the worst radiators. Ac- 
cording to Meloni, surfaces smoked or covered with lampblack, radi- 
ate most heat. If the power of radiation of such a surface be repre- 
sented by 100, that of glass will be 90 (it is therefore an excellent 
radiator), polished cast-iron, 25 ; poHshed wrought iron, 23 ; polished 
tin, 14 ; brass, 7 ; silver, 3. By tarnishing, or rusting metallic surfaces, 
their radiating power is increased. Leslie has shown that, compared 
with a smoke-blacked surface, as 100, clean bright lead is 19, while if 
tarnished, it is 45, If the actual radiating surface is metallic, it matters 
little what substance is under it. Glass covered with gold-leaf, is re- 
duced in its radiating power to the condition of a polished metal. If the 
bright, planished, metallic surface is in any way dulled or roughened, 
as by scratching or rusting, its power of throwing off heat is greatly 
increased. Indeed, if the polished surface is only covered, the same 
effect is produced. Rumfoed took two similar brass cylinders, cov- 
ered one with a tight investment of linen, and left the other naked* 
he then filled each with hot water, and found that the same amount of 



30 RADIATION AND ITS EFFECTS. 

heat whicli was thrown off by the covered cylinder in 36^ minutes^ 
required 55 minutes to radiate from the naked cylinder. 

27. How Polishing affects Surfaces. — Dr. Laedner says "the diminu- 
tion of radiating power, \yhich ordinarily accompanies increased polish 
of surface, is not a consequence of the pohsh in itself, but of the in- 
creased density of the outer surface^ produced by the act of polishing; 
and the effect of roughening is to be ascribed to the removal of the 
outer and denser coating." 

28. Best Mode of Confining and Retaining Heat, — These principles show 
us how best to enclose and retain heat when we wish to prevent waste 
from radiation. Glass, porcelain, and stone ware surfaces, radiate 
freely : vessels of these materials are not the best to preserve foods 
and fluids hot at table. They should either be of polished metal, or 
have bright metallic covers, which will confine the heat. Bright tea- 
urns and coflee-pots are best to retain their contents hot ; and a tea- 
kettle keeps hot water much more effectually if clean and bright, than 
if covered with soot, though it is much harder to boil. Pipes intended 
to convey heat should be bright and smooth, while those designed to 
radiate or expend it, should be rough. For the same reason, polished 
stoves and stove-pipes are less useful in warming rooms than those 
with rougher surfaces. 

29. Color of Surfaces docs not influence Radiation. — It is very generally 
supposed that the color of a substance influences the escape of heat 
from it. But the experiments of Dr. Bache have shown that this is 
a popular fallacy. He has proved that color exerts no control on the 
radiation of non-luminous heat, or such as is unaccompanied with light. 
A body will emit heat from a white or black surface with equal 
facility. 

30. Heat thrown off from Bodies. — Radiant heat striking upon bodies, 
if it is not permitted to pass instantly through them in straight lines, 
is either abso^hed or reflected. If reflected, it is instantaneously thrown 
back from the surface of the body, and therefore does not enter to 
warm it. If absorbed, it is gradually taken into the substance, and 
raises its temperature. A bright metallic surface will reflect the heat 
rays and itself remain quite cold. As heat cannot get out through a 
bright surface, so it cannot get in through it. AH the heat that is 
thrown upon such a body, is either reflected or absorbed ; that which is 
not disposed of one way goes tlie other. If half of it is absorbed, the 
other half will be reflected. Glass absorbs 90 per cent, and reflects 10, 
while polished silver reflects 97 per cent, and absorbs but 3. A good 
absorbing surface is a bad reflecting surface, and a good reflector is a 



THEORY OF HEAT-EXCHANGES. 31 

bad absorber. So a good radiating surface absorbs well and reflects 
badly, wbile a bad radiating surface absorbs badly but reflects well, 
Tbe density, or polish of a surface controls tbe admission as well as 
the escape of radiant beat. Two kinds of heat may thus pass in straight 
lines from a body — radiant heat and reflected heat. The former comes 
from within, and therefore cools it ; the latter strikes against it, and 
rebounds without either warming or cooling it. 

31. Color of Surface inflnences the admission of Heat. — We have seen 
(29) that color has no influence over radiating surfaces ; but the power 
which bodies possess of atsorling heat, depends very much upon color. 
Feanklin spread differently colored pieces of cloth upon snow in the 
sunshine. That of the black color sunk farthest below the surface ; 
which showed that it melted the most snow, and consequently received 
most heat. The blue piece sunk to a less depth, the brown still less, 
and the white hardly at all, which showed that it absorbed least heat. 
Hence, by scattering soot over snow, its melting may be hastened : it 
will absorb more of the solar heat. A dark-colored soil warms easier 
in spring, is earlier, and has a higher temperature during summer, than 
one in other respects similar but of a lighter color. Darkening a soil 
in color, therefore, is equivalent to removing it farther south. Grapes, 
and other fruits, placed against a dark wall, wiU mature or ripen 
earlier than if against light-colored walls, because, for the same reason, 
they are warmer. So, also, in the matter of clothing, white throws 
off the solar heat, while black absorbs it. 

32. Exchanges of Heat— it escapes from all Snbstances. — It has been 
stated that, down to 200° below the freezing point of water, substances 
contain heat and may part with it : and as we know of no means by 
which heat can be absolutely enclosed or confined within bodies, all 
are regarded as not only possessing the power of radiation, but as actu- 
ally exercising it. Kays of heat pass away in every direction, from all 
points of the surfaces of all bodies. When several objects of various 
temperatures, some cold and some hot, are placed near each other, 
their temperatures gradually approach the same degree, and after a 
time they will be found to have reached it. Now all these bodies are 
supposed to be constantly radiating heat to each other, and hence con- 
stantly exchanging it. If we place a cannon-ball at a temperature of 
1000° or a red heat, beside another at 100°, it will part with its heat 
rapidly to the latter, as illustrated by the radiant lines in Fig. 5. But 
the ball at 100° also radiates its heat, although more a, jwly, and thus 
returns a portion to the hotter ball ; so that there is an exchange estab- 
lished. But if a ball of ice at o2° be placed beside the cannon-ball at 




32 EADIATION AND ITS EFFECTS. 

100°, the same thing takes place, only in a less intense degree; and if 
Fis. 5. an ice-ball from the 

Arctic region at 100" 
below the freezing 
point, were placed be- 
side another at 32°, ex- 
actly the same thing 
would occur. Thus all 
bodies are constantly 

Exchanges of heat ; it radiates from bodies at all temper- interchanging heat and 

tending to equalization. 

33. Starlight Nights colder than clondyOnes. — The various objects 
upon the earth's surface, are not only continually radiating their heat 
to each other, but also upward through the air into space. If there 
be clouds above, they throw it back again to the eai'th's surface ; but 
if the sky is cloudless, the heat streams away into space, and there is 
none returned. At night, therefore, when there is no heat coming 
down from the sun, and no clouds to prevent its escape from the earth, 
the temperature of the earth's surface and the objects thereon, falls. 
Those which radiate best, cool fastest, and sink to the lowest tempera- 
ture. Clear, starlight nights are thus colder than cloudy nights ; and 
although more pleasant and inviting for evening walks, require that " 
more clothing should be worn. 

34. How Dew is Prodnced. — The cause of dew was not understood 
until lately. Many were persuaded that it came out of tlie earth; 
while others thought it fell as a fine rain from the elevated regions of 
the atmosphere. The alchemists regarded it as an exudation from the 
stars. They believed dew-water contained celestial principles, and 
tried to obtain gold from it. The problem was solved about forty 
years ago, by Dr. Wells, who first considered it in connection with 
the radiation of heat. The air contains moisture in the state of invis- 
ible vapor ; if its temperature be high, it will hold more moisture, if 
Iow,less(28G). "When, therefore, the air is suflaciently cooled, its moisture 
is condensed, and appears as drops, of water. These are often seen in 
summer days upon the outside of the pitcher of cold water ; improp 
erly called the sioeating of the pitcher. The moisture that is seen 
trickling down the window-pane in winter, is condensed from the 
vapor of the air in the room, by the outward escape of heat from the 
glass, and the consequent cooling of the air in contact with it inside. 
When, therefore, by nightly radiation, any objects upon the earth's 
Burface have become so cold as to cool the air in contact with them, 



IT EXPLAINS THE CAUSE OP DEW. 33 

sufficiently to condense its moisture, dew is formed, and the degree of 
temperature at which this efiect takes place, is known as tlie dew-point. 

35. Conditions of tlie Deposit of Dew. — Every calm and clear night 
the surface of the ground cools by radiation from 10" to 20°. But 
this surface is composed of various objects, which radiate unequally. 
Some part with their heat so rapidly as to cool the air down to the 
point of condensation, and dew is deposited upon them. Others ra- 
diate so slowly that their temperatures do not sink to the dew point, 
and no dew is formed upon them. Good radiators become covered 
Avith dew, while bad radiators remain dry. Grass, for example, is an 
excellent radiator, and it receives dew copiously, while under the same 
circumstances, stones, being bad radiators, are not moistened. Dew 
is deposited from a stratum of air only a few inches thick, which is 
condensed by contact with the cold body. If, however, that stratum 
of air is moved away before it gets sufficiently cooled, no dew will be 
formed. Hence, when the air is in motion, as on windy nights, there 
is no dew. Fall of temperature always precedes the formation of dew, 
and the greater the fall, the heavier the dews ; the quantity of moist- 
ure in the atmosphere, in both cases being the same. Farmers very 
well know that nights with heavy dews are very cold ; but the cold 
is the cause^ not the effect^ of the dew. The moister the air is, with 
the same descent of temperature, the more dew falls. Thus, arid 
deserts are dewless, notwithstanding the intense nightly radiation. 

36. Exchanges of Heat may prevent Dew. — We have noticed Peevost'8 
theory of the exchanges of heat, by which, all bodies are assumed to 
radiate heat to each other constantly (32). This explains why littlf 
or no dew is found under trees. While the grass radiates upward, the 
foliage radiates downward, and thus checks cooling. For this reason, 
no dew is precipitated on cloudy nights. As objects radiate upward, 
the clouds radiate back again, and prevent the falling of the tempera- 
ture. More dew falls upon the summits of mountains, where objects 
are most open to the sky, than in valleys, where the angle of radiation 
or access to the open heavens is much less. Objects protected in any 
way from exposure to the sky, are, to that extent, guarded from dew. 

37. Frost Cansed in the same way as Dew. — As a certain amount of 
cooling, deposits moisture from the air, more still, freezes it ; and 
hence, yVosi or frozen dew. This extreme cooling is often hurtful to 
vegetation, and during the serene nights of spring, tender plants are 
often killed, as is frequently the case with immature fruits and grain 
of autumn. Here, sgain, all circumstances which oppose radiation, 
prevent the cooling. Vegetables, sheltered by trees, suffer less than 




34 COlSTDtJCTION OF HEAT. 

those not so protected. A thin covering of cloth or straw, preserves 
plants, as may also fires that fill the air with smoke. 

V. CONDUCTION OF HEAT AND ITS EFFECTS. 

38. Heat creeps slowly tlirongb some Bodies. — If we place one end of 
a bar of metal in a fire, that end becomes hotter than the other parts 
of the bar. But this effect is only temporary ; the heat will gradually 
pass through it, being communicated from particle to particle, until 

Fig. 6. the other extremity becomes 

heated. This is easily shown 
by taking several marbles, and 
sticking them to an iron or 
copper wire with wax Tig. 
6. If now heat is applied 
to one end of the wire, it 

The balls drop successively as the heat moves t ^^ . , , 

along the rod. gradually travels along, the 

wax is melted, and the marbles drop off successively. The heat in 
this case is conducted by the metal. 

39. Diflferent Substances condnct at different Rates. — Heat diffuses in 
this manner, at very unequal speed through different substances. If 
we hold one end of a nail in a candle flame, it soon gets so hot as to 
burn the fingers ; while we can fuse the end of a glass rod in a lamp, 
although holding it within an inch of the melting extremity. Iron 
thus conducts heat much better than glass. Those substances through 
which heat is diffused most rapidly, are called good conductors, while ' 
those through which it passes slowly, are had conductors. In general, 
the denser a body is, — that is, the closer are its particles,^the better 
does it conduct heat; while the more porous, soft, loose and spongy 
it is, the lower is its conducting power. The metals, therefore, are the 
best conductors, while bodies of a fibrous nature, such as hair, wool, 
feathers, and down, are the worst conductors of heat. 

40. Ramford's Scale of Condnctors. — Rtimfoed arranged bodies in 
the following order, their conducting power progressively diminishing 
as the list proceeds. Gold, silver, copper, iron, zinc, tin, lead, glass, 
marble, porcelain, clay, woods, fat or oil, snow, air, silk, wood-ashes, 
charcoal, lint, cotton, lampblack, wool, raw silk, fur. 

41. Condoeting Power of Building Materials. — Bad conductors, — non- 
conductors, as they are called, — afford the best barriers to heat, and 
they are employed when it is desired to confine it. In winter, nature 
protects the earth and crops from excessive cold, by a layer of non- 



EFFECTS OF NOX-COKDUCTING SUBSTANCES. 35 

condacting snow. The birds, she protects by feathery and downy plu- 
mage ; quadrupeds, by haii*, wool, fur ; — and even the trees, by porous, 
non-conducting bark. In the management of heat, man finds the 
variation in the conducting powers of bodies, of the highest import- 
ance. In building houses, the worst conductors are the best materials 
for the walls. "While they promote warmth in winter, by retaining 
the heat generated by fires within, they are favorable to coolness in 
summer, by excluding the external heat. Hutohinson examined 
some building materials, and ascertained their conducting powers 
to be as follows, omitting fractions. (Slate being taken as 100.) 
Marble 75 to 58, fire brick 62, stock brick 60, oak wood 34, 
lath and plaster 25, plaster of Paris 20, plaster and sand 18. The 
Lard woods conduct better than soft, and green woods better than 
dry. Dry straw, leaves, &c., are good non-conductors, and are used 
to cover tender plants in winter, but if wetted, they convey heat 
much better. 

42, Non-condncting properties of Air. — Air is one of the most perfect 
non-conductors; Kumfoed thinks it is the best of all. The conduct- 
ing power of air, however, is greatly increased by moisture. If we 
represent the power of common dry air to conduct heat, by 80, its 
power, when loaded with moisture, rises to 230, — it is nearly trebled. 
For this reason, damp air feels colder to the body — it conducts away its 
heat faster. Those substances which enclose and contain air, as pow- 
dered charcoal, tan-bark, sawdust, chafi", &c., are good non-conductors 
of heat. Sawdust is an excellent bar to heat ; it should not be too 
much pressed together, as then, the particles, being in too close con- 
tact, conduct better : — nor too loose, as the air circulates through it, 
and thus conveys the heat. A layer of air between double windows, 
checks the escape of heat, but we do not, in such a case, avail our- 
selves of its perfect non-conducting power, otherwise we might use 
it to enclose ice-houses, &c. It is easily set in motion (97), and thus 
becomes a ready transporter of heat. Loose, porous bodies are filled 
with it, and they act as non-conductors by preventing its motion, 

43. Non-confllicting Properties of Clotliing, — Winter apparel is made 
of non-conduoting woollen fabrics, which prevent the escape of heat 
from the body. Cotton carries off the heat faster than wool ; and 
linen still foster than cotton. Linen is pleasantest in summer to re- 
lieve the body of heat, but it cannot defend the system like flannel 
against the sudden changes of temperature in an inconstant climate. 
In local inflammation of the body, linen is the best for dressings and 
applications, as it is a better conductor, and therefore cooler than cot- 



86 CONVEYANCE OF HEAT. 

ton.* The high non-conducting power of the woollens, is shown 
by the common practice of preserving ice in hot weather, by simply 
wrapping it in flannel. 

44. Onr Sensations of Heat depend upon Condnction. — The sense of 
touch is an unreliable guide to the degree of heat, because substances 
are so diverse in conducting power. The badly conducting carpet 
feels warmer to the naked feet than the better conducting oilcloth, 
because the latter will carry away the heat faster from the skin, al- 
though both are at exactly the same temperature. This influence of 
conduction over sensation, as also the remarkable difference of con- 
ducting power among solids, liquids, and gases, may be shown in a 
forcible manner. If the hand be placed upon metal at 120° it will be 
burned, owing to the rapidity with which the heat enters the flesh. 
"Water will not scald, provided the hand be kept in it without motion, 
till it reaches the temperature of 150° ; while the contact of dir at 
260° or 300° may be endured. Sir Joseph Banks went into a room, 
heated to 260°, and remained there a considerable time without incon- 
venience. The particles of air are so far asunder, that the heat crosses 
their inter-spaces with difiiculty ; and as but few of them can come 
in contact with the body at once, the amount of heat that they can 
impart is comparatively small. 

VI. HEAT CONVEYED BY MOVING MATTER. 

45. It is carried by Particles in Motion. — The freedom Avith which the 
particles of liquids and gases move among each other, is another source 
of the motion of heat. Water conducts heat but very imperfectly. 
If a glass tube filled with water, be inclined over a lamp, so that the 

flame is applied at the upper end Fig. 7, the 
water will boil at the top of the column, but 
below the point where the flame is applied, 
the temperature of the water will be but lit- 
tle elevated in a long time. The conduction 
of heat is not influenced by the position of the 
body along which it passes. It moves through 
_ _ a conductor as swiftly downward as upward, 

, ^ or horizontally. Had the heat, in this case, 

The water does not conduct ". 

the heat downwards. been conducted^ it would have travelled as 
readilj down the water column as upward. Yet all understand that 

* Linen is also test for dressing local inflammations, because its fibres are round and 
Bmooth, and therefore, less Irritating. The fibres of cotton are flat and angular, and of 
woollen, rough and jagged, and consequently, unfit for this purpose (795). 




ITS TEANSPOKTATION BY VATEK. 87 

a large amount of water may be heated by a small fire, if the heat 
be apijlied at the bottom. The cause of this is, that the lower layer 
of water in the vessel, being warmed, expands, becomes lighter, and 
for the same reason that a cork would rise, ascends through the mass 
of liquid above. Its place is taken by the colder liquid, which in 
turn warms, expands and ascends ; and thus currents are formed, by 
which the heat is conveyed upward, and diifused through the mass. 
This mode of heat movement is hence called convection of heat. 

46. How the Watcr-cnrrents may be sliown. — The circulation thus pro- 
duced by ascending and descending currents, may be beautifully seen 
by nearly filling a pretty large glass flask with water, and dropping 
into it a few small pieces of solid litmus {a cTieap^ blue coloring sui- 
stance), which sink through the liquid. On applying heat to the bot- 
tom of the vessel by a small lamp, a central current of water, made 
visible by the blue tint it has acquired from the litmus, is seen rising 
to the surface of the liquid, when it bends . -pia s 

over in every direction like the branches of 
the palm tree, and forms a number of descending 
currents, which travel downward near the 
sides of the vessel JFig. 8. Two causes 
operate here to distribute the heat. The 
warm liquid constantly conveys it away, and 
at the same time, the colder particles are con- 
tinually brought back to the source of heat, 
at the bottom. Exactly the same thing takes 
place when air is heated ; it expands, becomes 
lighter, rises in currents, and carries with it 
the heat. We shall refer to this principle 

again, when speaking of the contrivances for 

warming rooms. ^""*'°* bHomnt '° ^"^"^ 

VII. VARIOUS PROPERTIES AND EFFECTS OF HEAT. 

47. Heat added to Solids, llqaefies them.— Not only is the size of 
bodies influenced by heat, but also their state, or form. As heat enters 
a solid body, its particles are forced asunder, until at length they lose 
their cohesive hold of each other, and fall down into the Hquid state. 
The particles have become loosened and detached, and glide freely 
among each other in all directions. Carbon and pure alumina are 
the only substances that have not been liquefied by any amount of 
heat yet applied. Some solids, at a given point of temperature, enter 




38 VARIOUS EFFECTS OF HEAT. 

suddenly iuto the liquid state, aud others pass gradually through an 
intermediate stage of pastiness or softeuing. 

48. Melting Points. — That degree of temperature Avhich is required 
to melt a substance, is called its melting or fusing point. The com- 
mon temperature of the air is sufficient to melt some substances. 
From this point all along up to the highest heat, at which carbon re- 
fuses to liquefy, various substances melt at different temperatures, 
showing that each requires its particular dose of heat to throw it into 
the liquid state. Thus, mercury is a liquid at common temperatures, 
and is the only metal that exhibits this peculiarity. Phosphorus melts 
at 108°, wax 142°, sulphur 226°, sugar cane 320°, tin 442°, lead 612% 
zinc 773°, silver 1873°, gold 2016°, iron 2800°. Liquidity seems thus 
to be produced by the combination of solids with heat. Take the 
heat from a liquid and it solidifies. Take away the heat from water 
until it falls to 32°, and it becomes solid water, or ice. If kept per- 
fectly still, it may be lowered below 32° before the atoms lock to- 
gether into the crystalline or congealed state ; but if the water is 
jarred or agitated, crystalline ice results at that temperature. Heat 
taken from mercury until it falls to 39° below zero, causes it to harden 
into a solid, ringing raGtal— freezes it. - 180° of heat taken from alco- 
hol, do not freeze, but make it thick and oily. As heat combined 
with solids produces liquids, so heat combined with liquids produces 
vapors or gases. Heat added to ice generates water — added to water 
generates steam. The heat which converts solids into liquids, is called 
caloric of fluidity, and as gases are known as elastic fluids, the heat 
which changes liquids to gases is called caloric of elasticity. 

49. What is meant by Specific Heat. — If we take equal weights of 
different substances, and expose them to the same sources of heat, 
they do not all receive it with equal readiness ; in the same length 
of time some will be much more warmed than others. If a lamp 
flame of a given size will raise the temperature of a pound of spirits 
of tui'pentine 50*^ in ten minutes, it will take tiDO flames of the same 
size to raise a poimd of water through the same temperature in the 
same time, or it will take the same flame twenty minutes, or twice as 
long. It is clear that the water in this case, in being raised through 
the same temperature, has received twice as much heat as the spirits 
of turpentine. If a flame of a certain size will heat a pound of mercury 
through a certain number of degrees in a certain time, it will take 30 
flames of the same heating power, to raise a pound of water through 
the same range of temperature in the same period ; to raise it through 
the same number of degrees, therefore, water requires thirty times 



WATER HOLDS LARGE QUANTITIES OF IT. 39 

the heat that mercury does. This would seem to show that diftereat 
bodies have diflerent capabihties of holding or containing heat, or, as 
it is usually said, they have different capacities for heat : and, as each 
Bubstance seems to take a peculiar or particular quantity for itself, 
that quantity is said to be its ' specific ' heat. The specific heat of 
water is greater than that^of any other substance. In ascending from 
a given lower to a higher point, it takes into itself or swallows up 
more heat than any other body ; and in cooling down through that 
temperature, as it contains more to impart, so it gives out more heat 
than any other body. If the specific heat of water is represented by 
1000, that of an equal weight of charcoal is 241, sulphur 203, glass 
198, iron 113.79, zinc 95.55, copper 95.15, mercury 83.32. 

50. Why Water was made to hold a large amount of Heat. — When we 
consider tbe extent to which water is distributed upon the earth, we 
see the wisdom of the arrangement by which it is made to hold a 
large amount of heat, and the necessity that it shoiild slowly receive, 
and tardily surrender what it possesses. Suppose that the water of 
oceans, lakes, rivers, and that large proportion of it contained in our 
own bodies, responded to changes of temperature, lost and acquired 
its heat as promptly as mercury : the thermal variations would be 
inconceivably more rapid than now, the slightest changes of weather 
would send their fatal undulations through all living systems, and the 
inconstant seas would freeze and thaw with the greatest facility. But 
now the large amount of heat accumulated in bodies of water during 
summer is given out at a slow and measured rate, the climate is 
moderated, and the transitions from heat to cold are gradual and 
I'egulated. 

51. Why Water Is so cooling when drank. — It is because water is 
capable of receiving so much heat, that it is better adapted than any 
other substance to quench thirst. A small quantity of it will go 
much further in absorbing the feverish heat of the mouth, and throat, 
than an equal amount of any other liquid. When swallowed and 
taken into the stomach, or when poured over the inflamed skin, it is 
the most grateful and cooling of all substances. For the same reason, 
a bottle of hot water will keep the feet warm much longer than a hot 
stone or block. 

52. Concealed or latent Heat. — AU changes in the densities of bodies 
by which their particles are forced into closer union, or to greater 
distances apart, are invariably accompanied by changes of heat. 
Caloric is supposed to be contained in bodies, something as water is 
held in a sponge — lodged in its cavities or pores. If a wet sponge ia 



t 







40 VARIOUS EFFECTS OF HEAT. 

compressed, water is squeezed out ; but, when it expands again, it 
will again imbibe the liquid. In like manner material substances, 
when condensed into less space, give out heat, and, when dilated, 
they take it in or absorb it. If a piece of cold iron is smartly ham- 
mered upon an anvil, its particles are forced closer together, and its 
heat is driven out of its concealment, the iron becomes hot. By 
suddenly condensing the air as in the instrument called the fire-syringe, 
p in which a close fitting piston is driven down a tube (Tig. 

[X^ 9), the condensed air gives out so much heat as to set fire 
to tinder, Now, before condensing the iron, or the air, in 
these cases, they appeared cold, the thermometer de- 
tected in them no heat; yet they contained heat, and 
condensation brought it out. As we cannot find it by 
[t-^tI the ordinary test, we infer that it was concealed or latent 
in the iron and air. Heat is capable, therefore, of be- 
coming lost or hidden in bodies, and then of again 
re-appearing under proper circumstances. We call this 
latent heat, because we must caU it something, and the 
term is convenient ; but we are probably very far from a 

Air condenser. , , . . i^ j.i ^ j. • xi 

true explanation oi the facts in the case. 
53. How much Concealed Heat Water holds. — "Whenever a solid is 
changed to a liquid, a certain amount of heat disappears — goes into 
the latent state. If we take a lump of ice at zero, fix a thermometer 
in it, and expose it to a source of heat, the mercury in the thermo- 
meter will be seen to gradually rise up to 32 degrees. It then becomes 
stationary, although the application of heat is continued. But another 
change now sets in — the ice begins to melt. "While this continues, 
the thermometer does not rise, and the water at the end of the melting 
is at exactly the same temperature that the ice was at its commence- 
ment. As soon, however, as the ice is all melted, the mercury begins 
again to ascend, and the water becomes warm. Now, all the heat 
which entered the ice to liquefy it while the mercury was standing 
still, went into retirement in the water which was produced — became 
latent. It is very easy to find out how much heat becomes thus 
hidden when ice changes to water. If we take an ounce of ice at 
32°, and an ounce of water at 174°, and add them together, the ice 
will melt and we shall have two ounces of water at 32°. The ounce 
of hot water, therefore, parted with 142° of its heat, which has disap- 
peared in melting the ice. 142° is thus the latent heat of fusion of 
ice, which is hidden in the resulting Avater. The quantity of latent 
beat absorbed by different solids in entering upon the liquid condition 



STABILITY OF FOKMS PEESERVED. 41 

is variable, but a certain amount disappears in all cases. Thus, if a 
mass of lead be heated to 594°, it will then become stationary, although 
the addition of heat is continued ; but the moment the temperature 
ceases to rise, it will begin to fuse, and the temperature will continue 
steadily at 594° untd the last particle of lead has been melted, when 
it will again begin to rise. Those who have attempted to procure hot 
water from snow for culinary purposes, know by the delay of the 
result the great loss of heat which is involved. The heat necessary 
simply to melt 100 pounds of ice, without raising its temperature a 
single degree, would be sufficient to raise more than 80 pounds of ice- 
cold water up to boiling. 

54. Beneficial Effects of this Law. — ^This law of the latent heat of 
liquidity, operates admirably to preserve the /or7ns of material objects 
against the eftects of fluctuating temperatures.. The stability of bodies 
is too important a circumstance, and their liquefaction too consider- 
able an event, to be made dependent upon transient causes. If, when 
ice is at 32°, the addition of one degree of heat would raise it to 33°, 
and thus throw it into the liquid form, all the accumulated snows of 
winter might be turned almost in an hour into floods of water, by 
which whole countries would be inundated. But so large a quantity 
of heat is required to produce this change, that time must become an 
element of the process ; the snows are melted gradually in spring, and 
all evil consequences prevented. 

55. Principle of Artificial Freezing. — A solid may be changed to a 
liquid without the direct addition of heat. Attraction or affinity may 
produce the change. Yet the same amount of heat is required to go 
into the latent state. Salts have a strong attraction for water. If we 
put some common salt or saltpetre into water at the common temper- 
ature, it will become colder. The salt in dissolviug, that is, in assum- 
ing the liquid state, must have heat ; it therefore takes it from the 
surrounding water, which, of course, becomes colder. A mixture of 
five parts sal-ammoniac and five of saltpetre, finely powdered, and put 
in nineteen parts of water, will sink its temperature from 50° to 10° ; 
that is, 40 degrees. "When snow is mixed with a third of its weight of 
salt, it is quickly melted. The powerful attraction of the salt forces 
the snow into a liquid state ; but it cannot take on this state without 
robbing surrounding bodies of the heat necessary to its fluidity. Ices 
for the table are made in summer by mixing together pounded ice and 
salt, and immersing the cream or other liquid to be frozen (contained 
in a thin metallic vessel,) into the cold brine, produced by the melting 
of the ice and salt. A convenient method of freezing a little water 



42 VARIOUS EFFECTS OF UEAT. 

■without the use of ice, is to drench powdered sulphate of soda (glauber's 
salt) with mm-iatic acid. The salt dissolves to a greater extent in this 
acid than in water, and the temperature may sink from 50° to zero. 
The vessel in which the mixture is made, becomes covered with frost ; 
and water in a tube, immersed in it, becomes speedily frozen. 

56. Freezing literates Heat. — If the change of a solid to a liquid ab- 
sorls heat, the change of that liquid back again to the solid state, must 
liberate it. If the liquefying process swallows up heat, the solidifying 
process must produce the contrary effect — set it free again. As the 
thawing of snow and ice in spring, is delayed by the large amount of 
heat that must be stored away in the forming water, so the freezing 
processes of autumn are delayed, and the warm, season prolonged, by 
the large quantities of heat that escape into the air by the changing of 
water to ice. The same principle is made available to prevent the 
freezing of vegetables, fruits, &c., in cellars during intense cold weather. 
Pails or tubs of water are introduced, which, in freezing, give out 
sufficient heat to raise the temperature of the room several degrees. 
Freezing is thus made a means of wanning. 

57. Evaporation of Water. — "Water, at the surface, is constantly 
changing into invisible vapor, and rising into the air, which is called 
evajioration. It goes on at aU temperatures, no matter how cold the 
water is : indeed, evaporation constantly takes place from the surface 
of ice and snow. The ice upon the window often passes off as vapor, 
without taking on the intermediate form of water. StiU, the rate of 
evaporation increases as the temperature rises, so that it proceeds 
faster from the surface of waters in temperate, than in higher latitudes ; 
and more rapidly still at the equator. Evaporation into the air pro- 
ceeds more rapidly when the weather is dry, and is checked when it 
is damp. It is also hastened by a current. "Water will evaporate 
much quicker when the wind blows, than when the atmosphere is 
still, because, as fast as the air becomes loaded with moisture, it is re- 
moved and drier air takes its place. Extent of surface also facilitates 
evaporation. The same quantity of water will disappear much quicker 
in shallow pans, than in deep vessels. 

58. Wliat occurs in Boiling. — "When water is gradually heated in a 
vessel, minute bubbles may be seen slowly to rise through it. These 
consist of air, which is diffused through all natural waters, to the ex- 
tent of about four per cent., and which is partially expelled by heating. 
As the temperature increases, larger bubbles are formed at the bottom 
of the vessel, which rise a little way, and are then crushed in and dis- 
appear. These bubbles consist of vaporized water, or steam, which ia 



CONDITIONS WHICH INFLUENCE BOILING. 



43 



formed in the hottest part of the vessel ; but as they rise through the 
colder water above, are cooled and condensed. The simmering or singing 
sound of vessels upon the fire just before boiling, is supposed to be caused 
by vibratory movements produced in the liquid by the formation and 
collapse of these vapor bubbles. As the heating continues, these steam 
globules rise higher and higher, until they reach the surface and escape 
into the air. This causes that agitation of the liquid which is called 
boiling or ebullition. 

59. Influence of the Tessel in Boiling. — Different liquids boil at differ- 
ent temperatures : but the boiling point of each liquid varies with 
circumstances. The nature of the vessel has something to do Avith it, 
which depends upon its attraction for the water. To glass, and pol- 
ished metallic surfaces, it adheres with greater force than to vessels of 
rough surfaces. Before the water can be changed to vapor in boiling, 
this adhesion must first be overcome. "Water upon the surface of oil, 
boils two degrees below water in a glass vessel, in consequence of the 
oil having no attraction for the water. 

60. Measuring tlie Pressure of the Air. — Aij* has weight like visible 
ponderable matter, and presses down upon the surface of water the 
same as upon the ground. The pressure of the air is measured by a 
barometer^ which is simply a glass tube about Fio. lo. 

a yard long, closed at one end, filled with 
mercury, and then inverted with its open 
end in a vessel of mercury, as shown in 
Fig. 10. The liquid metal in the tube, is thus 
balanced against the air outside, and falls to 
a point upon the scale, which exactly indi- 
cates the pressure of the air. A column of 
atmosphere from the ground to its upper 
limit, is about as heavy as a column of mer- 
cury 30 inches high. We represent in the 
figure, but a single column of air pressing 
down upon the mercury; but we must re- 
member that its surface is completely cov- 
ered by such columns of air. Of course, the 
empty space or vacuum in the upper part of the tube permits the mer- 
cury to rise and fall without disturbance. From various causes the 
weight of the atmosphere varies ; when it is heavier, it presses harder 
upon the mercury, and drives it up ; when it is lighter, the mercury 
falls. The ordinary fluctuations of atmospheric pressure, cause the 
mercury to play along a scale of some two inches. As there is only a 



Vacuum, 
place of no 
pressure. 




Barometer tube 



44 VARIOUS EFFECTS OF HEAT. 

certain quantity of air to press dowa upon tlie earth, in g^^iQg up a 
mountain we leave much of it below us: of course, what remains 
above, is lighter, and presses with less weight. Hence, in ascending 
a mountain, the mercury in the barometer sinks in proportion as we 
rise higher. 

61. Influence of Air-pressure upon Boiling. — It is reported by travel- 
lers tliat, upon high mountains, meat cannot be cooked by the common 
method of boiling. The reason is, that the boiling water is not hot 
enough ; and the reason of that is that the pressure of the air being 
partially taken off, the water finds less resistance to rising into vapor, 
and a lower degree of heat produces the effect. The boiling point 
thus fluctuates with the barometric column : the natural variations of 
atmospheric pressure, at the same level, make a difference of 4| de- 
grees in the boiling point of water. 

62. Employment of tbe Principle in Refining Sugar. — It is often useful 
to boil off liquids at low temperatures. In order to change coarse, 
brown sugar into refined, white sugar, it has to be dissolved and 
purified. It is then reproduced by evaporating away the water. But 
the heat of the common boiling point is too great. So the refiner 
pumps out the air from above the boiling pans, by means of a steam- 
engine. The pressure is taken off", and the water boils away at a low 
temperature, leaving the sugar crystals perfect. 

63. Elevation of the Boiling Point. — If the weight of air pressing 
upon a liquid affects its boiling point, for the same reason the weight 
of the liquid itself^ must affect it. When salts are dissolved in water, 
they render it heavier, and its boiling point is always raised. Some 
salts, however, raise it more than others. Water saturated with com- 
mon salt (100 water to 30 salt)^ boils at 224° ; saturated with nitrate 
of potash ( 100 water to 74 salt)^ it boils at 238° ; with chloride oi 
calcium, at 264°. Ether boils at 96° (blood 7iea()\ alcohol, at 174°; 
turpentine, at 316°; mercury, at 662°. The viscidity of a liquid, or 
the glutinous coherence of its particles is opposed to its free ebullition. 

C4. Spheroidal state of Water. — Water in contact with highly heated 
metallic surfaces does not boil or vaporize. AH may have noticed it 
dancing or darting about in globules upon a hot stove. Tbe reason 
offered why a globule does not evaporate from a red-hot surface is, 
that a stratum of steam is formed under it, which props it up, so that 
it is not really in contact with the iron ; and steam being a noncon- 
ductor, cuts off also the heat. Water enters upon the spheroidal state 
between 288° and 340° of the hot surface : but when the temper- 
ature falls, the steam no longer sustains the drop ; it is brought into 



ITS RELATION TO BOILING. 



45 



contact with the iron, and is at once exploded into vapor. This prin- 
ciple is made available in the laundry in judging of the degree of heat. 
The temperature of the smoothing-iron is determined by its effects 
upon a drop of saliva let fall upon it. If the drop adheres, wets the 
iron, and is rapidly vaporized, the temperature is considered low; 
but if it run along the surface of the metal, it is regarded as suf- 
ficiently hot. 

65. But little Heat reqnired to maintaia Boiling. — If a liquid be con- 
fined in a sufficiently strong vessel, so that its vapor cannot escape, it 
may bo heated to any desired point of temperature ; though at high 
heats, vapors acquire such an expansive and explosive energy as to 
burst vessels of the greatest strength. But if the liquid be exposed to 
the ail*, it is impossible to raise its temperature above its natural boil- 
ing point. All the heat that is added after boiling commences, is car- 
ried away by the vapor. The rapidity with which water is raised to 
the boiling point, depends upon the amount of heat which is made to 
enter it. But when this point is reached, a comparatively small quan- 
tity of heat will maintain it there just as well as more. Water boiling 
violently, is not a particle hotter than that which boils moderately. 
When water is brought to the boiling point, the fire may be at once 
reduced. Attention to this fact would save fuel in many culinary 
operations, 

G6. Double Vessels to Regulate Heat. — If we have a substance which, 
placed directly over the fire, would receive an indefinite quantity of 
heat, but which we desire to raise only to a Fig. ii. 

certain temperature, we place it in a vessel 
surrounded by another vessel ; the outer one 
being filled with a liquid which boils at the 
desired temperature. Heokee's farina ket- 
tle. Fig. 11, is a culinary contrivance of 
this kind. The outer vessel is fiUed with 
water, while the inner one contains the 
material to be cooked, which, of course, can- 
not be heated higher than the boiling point, 
and is therefore protected from burning. By 
using any of the salt solutions mentioned 
(63), higher heats may be communicated to 
the internal vessel. 

67. Wliy Puddings, Pies, &c., cool slowly. 
We have seen that water is a bad conductor of heat ; that is, heat does 
not readily pass across its intervening spaces, from particle to particle, 




Section of a culinary bath : 
opening to introduce water. 



46 VABIOUS EFFECTS OF HEAT. 

and so become diffused tlirough it. "We do not, therefore, heat it b}' 
conduction, but by currents produced within it (46), which distribute 
and commingle the heat throughout its mass. It cools in the same 
way. As the particles at the surface or sides lose their heat, they fall 
to the bottom, and others succeed them. If the particles of water 
could remain stationary, it would be slow and difficult to heat, and 
equally slow to cool. For this reason soups, puddings, pies, &c., which 
contain large amounts of hot water, so enclosed and detained in their 
places that they are not free to circulate, and therefore, are not in a 
condition to lose their heat, keep hot longer, and cool slower than 
equal bulks of simple fluids. 

68, Concealed Heat of Vapor. — As the liquid state is the result of 
heat combined with solids, the vaporous state is the further result 
of heat combined with liquids. Enormous amounts of heat are 
necessary to convert liquids into vapor, but the vapors are no hotter, 
according to the thermometer, than the liquids were ; they are, there- 
fore, reservoirs of insensible heat. AU the heat which is necessary to 
boil ofl:" a liquid, becomes latent in its vapor. The heat that thus 
enters the boiling liquid without raising its temperature, must go 
somewhere. It is not sensible in the vapor which ascends from its 
surface, for that is no hotter than the liquid from which it came. It 
is contained in the vapor, for it may aU be again recovered from it. 
The quantity of heat which becomes latent in the process of evapora- 
tion, is very large. "With the same intensity of heat it takes 5^ times 
as long to evaporate a pound of water, as it does to raise it from i 
freezing to boiling ; it therefore receives 5^ times as much heat. If, 
therefore, 180° were required to boil the pound of water, 1000° are 
required to change it into a pound of vapor ; but, as the pound of 
vapor is no hotter than the pound of water, 1000° of heat must of 
course be concealed in it. The latent heat of steam is then 1000° ; 
when condensed, it surrenders that 1000° of heat. The condensation 
of a pound of steam will raise 5^ pounds of water from the freezing 
to the boiling point. This fact makes steam a valuable agent for 
transporting heat, as is done by means of steam pipes for warming 
buildings (129). "Wherever condensed, it liberates large quantities of 
boat. 

69. Coding cflTcct of Evaporation. — ^Evaporation is therefore a cooling 
process — it buries or temporarily destroys active heat. For this reason 
damp soils, although in all other respects like dry ones, are colder. 
Evaporation dissipates the heat which falls upon them. The heat 
poured down from the sun in torrid regions would be intolerable, 



ITS RELATION TO EVAPORATION. 41 

were it not for the cooling effect of rapid evaporation. Apartments 
are cooled in hot countries by evaporation, which proceeds from wet 
curtains. The skin of the body contains millions of little microscopic 
pores, through which water {perspiration) is constantly pouring out 
to the surface. As it then evaporates into the air and absorbs 
heat, it becomes a powerful cooling agency and regulator of bodily 
temperature ; while the vapor, which escapes from the breath, exerta 
a cooling effect within the body. It is very interesting to observe 
how the great capacity of liquid water for heat, makes it so gratefully 
cooling as it enters the body ; and how its still greater capacity for 
heat, when passing from the liquid state to the condition of vapor, 
enables it so constantly to bear away from us the germs of fever as it 
escapes from the system, in the form of insensible perspiration or 
vapor. The cooling effect of fanning the face, is partly due to the 
more rapid removal of the vapor of perspiration from the skin, and 
partly to the conduction of heat by the particles of moving air. 
Breezes cool us in the same way. "Wet floors become a source of cold, 
in roomsj through vaporization. The pernicious effect of wearing wet 
clothing is caused by the rapid evaporation which proceeds from it, 
thus robbing the body of large quantities of heat. When a person is 
obliged to remain in wet clothing, evaporation may be stopped by 
putting on an outer garment, which cuts off the external air. 

70. Reason of " blowing Hot and Wowing Cold." — It was stated that 
when air or gases are condensed, heat is set free ; on the contrary, 
when they are expanded, their capacity for latent heat is increased, 
it is absorbed, and cold is produced. This is a main cause of the 
danger when streams of air reach us through cracks and apertures, 
although a part of the mischief is caused by conduction. This peril 
is expressed in the old distich — 

"If cold air reach you through a hole, 
Go make your will and mind your soul." 

Air, spouting in upon us in this manner, not only cools by conduction 
and evaporation, but, having been condensed in its passage through 
the chink, it expands again, and thus absorbs heat. This is also 
familiarly illustrated by the process of cooling and warming by tho 
breath. If we wish to cool any thing by breathing on it, the air is 
compressed by forcing it out through a narrow aperture between the 
lips ; as it then rarefies, it takes heat from any thing upon which it 
strikes. If we desire to warm any thing with the breath, as cold 
hands, for example, we open the mouth and impel upon it the warm 
air from the lungs without disturbance from compression. 



48 INFLUENCE OF HEAT UPON THE BOBT. 



VIII.— PHYSIOLOGICAL EFFECTS OF HEAT. 

71. Local inflnence of Heat npon the Body. — It has been noticed that 
the general eflect of heat upon bodies is to expand them (15). It acts 
in this way upon the living system, just as upon all other objects. The 
pleasant sensation of warmth is occasioned by an expansion of the 
vessels of the skin, and the liquids which they contain ; these are ren- 
dered less viscid and thick by heat, and made to flow more readily, 
which produces an agreeable feeling. If the application of heat to a 
part be continued, the surface becomes red. The diameters of the 
minute capillary blood-vessels are so expanded, that the red blood-disks 
are enabled to enter tubes which would not previously admit them. 
The temperature rises, and there is a slight swelling or increase of the 
volume of the part, owing partially to the dilatation of the solids and 
liquids, but cliiefly to the presence of an increased quantity of blood. 
The living tissues at the same time become more relaxed, soft and 
flexible, and allow rapid perspiration. More heat still produces greater 
expansion. There is a sense of pain, the organic structure is decom- 
posed, the liquids begin rapidly to dissipate in vapor, and the surface 
becomes inflamed, blistered, and burned. 

72. General inflnence of Heat npon the System. — The body is subject 
to the action of two kinds of stimulants. Vital stimulants are those 
external conditions, such as air, water, food and warmth, which are 
necessary to the maintenance of life. Medicinal or alterative stimulants 
are those agents or forces which produce temporary excitement within 
the system, but ultimately depress and exhaust it. Now, in the pro- 
portion that is necessary simply to maintain the system at its natural 
temperature, heat is a healthful, vital stimulant; but beyond this it 
becomes a disturbing, exhaustive, health-impairing agent. The first 
eftect in undue quantity is excitation ; the secondary efiect, exhaustion. 
In the first instance, sensibility is agreeably promoted, voluntary 
muscular movement assisted, and the mind's action somewhat exalted ; 
but to these effects succeed languor, relaxation, listlessness, indispo- 
sition to physical and mental labor, and tendency to sleep. The body 
possesses a powerful means of self-defence against excessive heat, in 
the cooling influence of surface evaporation (69), but this power of the 
system cannot be taxed with impunity. The rush of the circulation 
to the surface, and the increased transpiration and secretion of the 
skin, are accompanied by a necessary diminution in the activity of 
Bome of the internal organs. As the exhalation from the skin rises, 
the secretion of the kidneys and mucous membranes falls. The pre- 



EFFECTS OF SUDDEN CllANUKS FUEL. 49 

vailing maladies of hot climates may be referred to, in illustration of 
the effect of continued heat on the body. Fevers, diarrhava, dysen- 
tery, cholera, and liver diseases, may be regarded as the si^ecial mala- 
dies of the burning, equatorial regions. — (Pereiea.) 

73. Conseqnences of suddea Changes.— But the worst effect of exces- 
sive heat, is not always the immediate stimulation, and consequent ex- 
haustion which it induces ; it is the sudden exposure to various de- 
grees of cold which often follows, when the system is in a relaxed and 
depressed condition, that accomplishes tlie most serious mischief, lay- 
ing the train for so many cases of afflicting disease, and premature 
death. The effect of passing from an over-heated apartment out into 
a freezing air bath, is suddenly to check the cutaneous circulation, and 
drive the blood inward upon the vital organs, thus often engendering 
fatal internal disease. It is thought that a temperature from 60° to 
65° is, perhaps, the safest medium at which an apartment should be 
kept, so that the individual may not suffer from transition to external 
cold. If this temperature seem uncomfortably low, it is better to in- 
crease the apparel than to run up the heat, and risk the consequences 
of subsequent exposure. 

IX. ARTIFICIAL HEAT— PROPERTIES OF FUEL. 

Y4. Artificial heat may be produced in various ways, but the com- 
mon method is by combustion, which is a chemical operation carried 
on in the air. All the heat which we generate for household i)uri)0- 
ses, is caused by the clieniical action of air upon fuel. But what part 
of the air takes effect ? The main bulk of the air is composed of 
two elementary gases, oxygen and nitrogen. In every five gallons of 
air, there are 4 of nitrogen and 1 of oxygen, mixed and diflrused 
through each other (281). Nitrogen, when separated, proves to have 
no active qualities ; it cannot carry on combustion, — ^it puts out fire. 
Oxygen, on the contrary, when separated, proves to be endowed with 
wonderful chemical energy. A fire kindled in it, burns with unnatu- 
ral violence; its chemical powers constitute the active force of the 
air. The nitrogen dilutes and weakens it, thus restraining its ac- 
tivity. 

Y5. Composition of Fnel,— Office of Carbon.— Tlie fuel upon which 
oxygen of the air takes effect in the burning process, consists of vari- 
ous kinds of wood and coal. These are chiefly composed of three ele- 
ments — oxygen, hydrogen, and carbon, in various proportions. The 
oxygen they contain, contributes nothing to their value as fuel; fAai 
3 



50 PROPERTIES OP FUEL. 

depends upon the other elements : hence, the more oxygen, the less 
there can be of these other substances, and, of course, the poorer the 
fueh Carbon exists largely in aU woods and coals. Oxygen and hy- 
drogen, when in their free state, — that is, uncombined, are always 
gases ; they never appear as liquids or solids, and no one has yet been 
able to force them into these states. Carbon, on the other hand, is 
an unyielding solid. No chemist has ever yet been able to prepare 
either liquid carbon or gaseous carbon. At the intensest white heat, 
where nearly every other substance melts, or dissipates into vapor, 
carbon remains fixed. It is the solidifying element of fuel, and it is 
this property which makes our fires stationary. 

VG. Hydrogen, and its OflSce in Fael. — Hydrogen gas, the other ele- 
ment of fuel, when set free is the lightest substance known, being 14 
times lighter than air. It is of so light and volatile a nature, that it 
will combine with solid carbon, and even iron, and carry them up with 
it into the gaseous state. When ce«nbined with fuel, it is condensed 
down into a solid state, but in the act of burning, it is released, and 
escapes into the gaseous form. It therefore hums in motion, and it 
is this which produces flame. In all ordinary combustion, the flame 
is caused by the burning hydrogen, and the larger the quantity of this 
substance in fuel, the greater the flame it wiU yield when burnt. 

77. Why it is necessary to Idndle a Fire. — Now, for these two sub- 
stances, oxygen has powerful attractions, and combines with them, 
producing combustion and heat. Yet atmospheric oxygen is every 
where in contact with all kinds of fuel without setting them on fire. 
Why is this ? Because the natural attractions of these substances are 
so graduated, that they do not come into active play at low tempera- 
tures. If carbon combined with oxygen at common temperatures, 
with the same readiness and force that phosphorus does, wood and 
coal would be ignited like a match, at the slightest friction, and com- 
bustive processes would be ungovernable. But as man, all over the 
world, civilized and savage, is designed to develope and manage fire 
through the agency of these substances, their energies have been 
wisely restrained within the limits of universal safety. This makes it 
necessary to resort to some means, as friction or percussion, to gener- 
ate heat necessary to start conibustion, or kindle the fire. 

78. Products of Combustion. — When the combustive process has 
commenced, two things take place ; the fuel disappears, and the air ia 
changed. The substance of fuel is not destroyed, it only changes its 
shape, takes on the invisible form, and mounts into the air. Oxygen 
Bombines with carbon, both elements disappear, and a new product 



ITS CHEMICAL CONSTITUENTS. 51 

results — carbonic acid gas (293). As carbonic acid is thus given off 
every where by combustion, it is a constant and universal constituent 
of the atmosphere. It forms l-2000th of the air, and would increase 
in quantity, but it is constantly withdrawn by plants. "When pure, it 
extinguishes fire, and when mingled with the air it rapidly diminishes 
its power of sustaining combustion. "When oxygen combines with the 
hydrogen of fuel, it produces vapor of water, which rises with the 
carbonic acid and disperses through the air. 

79. Fuel is changed before it is bnrned. — In burning, oxygen does not 
combine directly with hydrogen and carbon, changing them at once 
to water and carbonic acid. The heat of combustion first decomposes 
the fuel and re- combines its atoms, forming various compounds 
tinder different circumstances, and it is with these that oxygen 
unites. They consist mainly of hydrogen and carbon, and are 
more abundant as the proportion of hydrogen in the fuel increases. 
It is rare that these products, thus distilled out of fuel in the burning 
process, are completely consumed by oxj^gen; a portion of them 
escapes, constituting smoke. 

80. Heating powers of Hydrogen and Carbon. — The proportion of 
carbon in fuel is always very much greater than that of hydrogen, but 
the amount of heat which they give out is not in proportion to their 
relative weights. A given weight of hydrogen, when burned, wiL 
produce three times as much heat as the same weight of carbon. A 
pound of charcoal, which is nearly pure carbon, in burning, produced 
sufficient heat to change 75 pounds of water from freezing to boiling ; 
while a pound of hydrogen yielded heat enough in burning, to change 
236.4: pounds through the same number of degrees. The heat is in 
proportion to the oxygen consumed ; the pound of hydrogen united 
with 8 pounds of oxygen ; while a pound of carbon took but 2| pounds 
of it. The heating power of fuel thus depends upon chemical com- 
position, but it is also influenced by other circumstances. 

81. How Moisture affects the Valne of Wood. — "When wood is newly 
cut, it contains a large quantity of water (sap), varying in different 
varieties, from 20 to 50 per cent. Trees contain more water in those 
seasons when the flow of sap is active, than when growth is suspend- 
ed ; and soft woods contain more than hard. Exposed to air a year, 
wood becomes air dried^ and parts with about half its water; 15 per 
cent, more may be expelled by artificial heat; but before it loses tho 
last of its moisture, it begins to decompose, or char. The presence of 
water in wood diminishes its value as fuel in tv>'0 ways ; it Innders 
and delays the combustive process, and wastes heat by evaporation. 



52 



PEOPEETIES OF FUEL. 



Suppose that 100 pounds of wood contain 80 of water, they have 
then but VO of true combustive material. "When burned, 1 pound 
of the wood will be expended in raising the temperature of the water 
to the boiling point, and 6 more in converting it into vapor ; making 
a loss of 7 pounds of real wood, or ■^\ of the combustive force. Be- 
sides this dead loss of 10 per cent, of fuel, the water present is an an- 
noyance by hindering free and rapid combustion. 

82. Heating Value of different kinds of Wood. — Equal weights of differ- 
ent varieties of wood in similar conditions, produce equal quantities 
of heat ; but it will not do to purchase wood by weight, on account 
of the varying quantity of its moisture. It is sold by measure ; but 
equal measures or bulks of wood do not yield equal amounts of heat. 
According to the careful experiments of Mr. Marcus Bull, the rela- 
tive heating values of equal bulks {cords) of several American woods, 
are expressed as follows; — shell-bark hickory being taken as 100. 



Shell-bark Hickory 
Pignut Hickory 
White Oak 
White Ash 
Dogwood 
Scrub Oak 
Witch Hazel 
Apple tree . 
Red Oak 
White Beech 
Black Walnut 
Black Birch 



100 
95 
81 
77 
75 
73 
72 
70 
69 
65 
65 



Yellow Oak . 
Hard Maple 
White Elm 
Eed Cedar 
Wild Cherry 
Yellow Pine 
Soft Maple . 
Chestnut . 
Yellow Poplar 
Butternut . 
White Birch 
White Pine 



60 
60 
5S 
56 
55 
54 
54 
52 
52 
51 
48 
42 



83. Soft and Hard Woods. — Some woods are softer and lighter than 
others,.the harder and heavier having their fibres more densely packed 
together. But the same species of wood may vary in density, accord- 
ing to the conditions of its growth. Those woods which grow in for- 
ests, or in rich, wet gi'ounds, are less consolidated than such as stand 
exposed in the open fields, or grow slowly upon dry, barren soils. 

84. Wliy Soft and Hsird Woods burn differently. — There are two stages 
in the burning of wood : in the first, heat comes chiefly from flame ; 
in the second, from red-hot coals. Soft woods are much more active 
in the first stage than hard; and hard woods more active in the 
second stage than soft. The soft woods burn with a voluminous 
flame, and leave but little coal ; while the hard woods produce less 
fla^iie, and yield a larger mass of coal. The cause of this is partly, 
that the soft woods, being loose and spongy, admit the air more freely, 
but it is chiefly owing to differences in chemical composition. Pure 



BURNING OF WOOD AND COAl,. 53 

woody fibre, or lignin, from all kinds of wood, lias exactly the saino 
composition ; a compound atom of it containing 12 atoms of carbon, 
10 of hydrogen, and 10 of oxygen — or there is just enough oxygen in 
it to combine with all its hydrogen and change it to water in burning. 
But in ordinary wood, the fibre is impure ; that is, associated with 
other substances which practically alter its composition. The hard 
woods are nearest in composition, to pure lignin, but the softer woods 
contain an excess of hydrogen. For this reason, they burn with more 
vehemence at first ; more carbon is taken up by the hydrogen, in pro- 
ducing flame and smoke, and the residue of coal is diminished. The 
common opinion, that soft wood yields less heat than hard {eqiml 
^Deights) is an error ; it burns quicker, but it gives out an intenser heat 
in less time, and is consequently better adapted to those uses where a 
vapid and concentrated heating effect is required. 

85. Charcoal as Fuel. — Charcoal is the part that remains, when wood 
has been slowly burned in pits or close vessels, with but a limited sup- 
ply of air, so that all its volatile or gaseous elements are expelled. 
Wood yields from 15 to 25 per cent, of its weight of charcoal ; the 
more the process is hastened, the less the product. When newly made, 
charcoal burns without flame, but it soon absorbs a considerable por- 
tion of moisture from the air, which it condenses within its pores. 
When this is burned, a portion of the water is decomposed, hydrogen 
is set free, and there is produced a small amount of flame. Being very 
light and porous, and its vacancies being filled with condensed oxygon, 
(811) it ignites readily, and consumes rapidly. Wood charcoal produces 
a larger amount of heat than equal weights of any other fuel. 

86. Mineral Coal as Fnel — Anthracite. — The pit coal which is dug from 
beds in the earth, is a kind of mineral charcoal. It gives evidence of 
having been derived from an ancient vegetation, which was by some 
unknown means buried in the earth, and there slowly charred. Indeed, 
the properties of the different varieties of coal, depend upon the degree 
to which this charring operation has been carried. In anthracite, 
which is the densest and stoniest of all, it has reached its last stage ; 
the volatile substances are nearly all expelled, so that nothing remains 
but pure carbon with a trace of sulphur, and the incombustible ash. 
From its great density, when we attempt to kindle it, instead of 
promptly taking fire, the heat is rapidly conducted away, so that the 
whole mass has to be raised together to the point of ignition. When 
once thoroughly fired, this coal burns with an intense heat for a long 
time, though less freely in a grate than in a stove. It is difficult in the 
grate to keep the whole mass of coal in a state of vivid redness, a." t.bp 



54 PROPERTIES OF FUEL. 

air conveys away so much heat from the surface of tlie fire as to coo^ 
it down below the point of combustion (114). Anthracite burns without 
flame, smoke, or soot, although with sulphurous vapors, which, when 
the draught is imperfect, or when burned in a stove, are liable to 
accumulate in the room, to the serious detriment of its inmates. The 
anthracite fire is objected to by many as causing headache, and other 
bad symptoms. Aside from its sulphurous emanations, the extreme in- 
tensity of its heat, undoubtedly, has a share in producing these elfects. 

87. Combnstion of Bitaminoas Co.al. — When the great natural process 
of underground charring is less advanced, the coals are iituminous; 
that is, they contain bitumen or pitch, a substance rich in hydrogen. 
These ignite readily, and burn with much flame and smoke. Those 
which contain the largest proportion of pitchy material, are known as 
' fat' bituminous coal, and in burning, they soften or melt down into a 
cake, (caMng coal) and stop the draught of air. Those with less hy- 
drogenous matter, are termed ' dry,' or ' semi-bituminous ' coal ; 
they burn freely without cementing or caking. Bituminous coals fur- 
nish illuminating gas by distillation in iron retorts ; a process of char- 
ring with entire exclusion of air. The residue left after charring bitu- 
minous coal, is called coke ; it is procured of the gas manufacturers 
and used as fuel, burning quietly like anthracite, though, owing to 
its sponginess, it is more easily kindled and yields less heat. Good 
bituminous coal burns freely and pleasantly in an open fire, with an 
agreeable, white flame, producing carbonic acid in large quantity, a 
small proportion of sulphurous vapor, and the common carbonaceous 
constituents of smoke (103). Its heat is much less violent than that 
of anthracite. 

88. Lignite or Brown Coal is that variety which seems to have been 
least charred, and stili retains the woody structure; its comba'^tive 
value is low. 

89. Heating Effects of the different Fuels.— The heating value of these 
fuels, when burned under the same circumstances, have been deter- 
mined as follows : One pound of wood charcoal will raise from the 
freezing to the boiling point, 73 pounds of water. One pound of min- 
eral coal will heat 60 pounds of water through the same number of 
degrees ; and one pound of dry wood, 35 pounds of water in the same 
way. These are the highest results obtained by careful experiments. 
In practice, we do not get so great a heating effect; and besides, the 
circumstances under which the fuel is burned, whether it be in a stove 
or fire-place, makes considerable difference in the result. 

90. Amonnt of Air required to consume Fuel. — As the weight of air 



ASCENT OF AIK THROUGH CHIMNEYS. 55 

necessary to bum fuel is vastly greater than the fuel itself, and as air 
is exceedingly light, it will be seen that immense bulks of it are con- 
sumed in combustion. It requires 11.46 pounds of air to burn one 
pound of charcoal ; and as one pound of air occupies nearly 13 cubic 
feet of space, the pound of charcoal wiU require about 150 cubic feet 
of air. One pound of mineral coal is burned by 9.26 pounds of air, or 
120 cubic feet; and one pound of dry wood consumes 5.90 pounds, or 
75 cubic feet of air. These are the smallest possible amounts that can 
be made to effect the combustion; as fuel is usually burned, much 
more is consumed. 

91. Too mnch Air binders Combustion. — Yet if the object is simply to 
•produce heat^ the contrivances we employ should be adapted to admit 
the least possible quantity of air beyond what actively carries forward 
the combustion. Excess of air becomes detrimental to the burning pro- 
cess, by conveying away heat which it does not generate, cooling the 
fuel, and checking the rate of combustion. Indeed, so much air may 
be projected upon a tire, as to cool it down below the burning point, 
and thus put it out as eftectuaUy as water (114). 

X.-AIR CURRENTS— ACTION AND MANAGEMENT OP CHIMNEYS. 

92. Canse of tbe Cbimncy Drangbt. — The candle flame tends upward ; 
its hot gases and the surrounding heated air rising in a vertical stream, 
which illustrates the universal tendency of warmed air. No matter 
how it is heated, it expands, because rarer and lighter, and is pressed 
npAvard by that which surrounds it. Not that heated air has any 
mysterious tendency to ascend, but there being less of it in the same 
space, the earth does not attract it downward with the same force that 
it does the denser and colder surrounding air. As the atmospheric 
particles move among each other with the most perfect freedom, the 
colder and heavier air takes the lower position, to which gravitation 
entitles it, and thus drives the warmer air upward. This upward 
tendency of rarified gases is tbe force made use of to supply our fires 
with the large amount of air which they demand. The fire is kindled 
at the bottom of a tube of iron or brick- work, called a flue or cJdmnei/. 
The atmospheric column within it is heated and rarified, and the outer 
air drives in to displace it. This, in its turn, is also heated and ascends ; 
a continuous current is established, and a stream of fresh air secured 
to maintain the combustion. The chimney also servos to remove from 
the apartment the noisome and poisonous products of combustion. 

93. Conditions of the Force of Draught.— The force of the chimney 



66 ACTION AND MANAGEMENT OF CHIMNEYS. 

draught depends upon the velocity of the rising current, and tliat again 
upon the ditference of weight between the column of air in the chim- 
ney, and one of equal size outside of it. Three circumstances influ- 
ence the force of draught : the temperature, length, and size of the air 
column within the chimney. The hotter it is, the higher it is, and the 
larger it is, within certain limits, the greater wiU be its ascensional 
force. All high chimney stacks, with large channels, containing 
highly rarified air, produce roaring draughts ; while if they be short 
and narrow, and their temperature low, the draught is proportionally 
enfeebled. Friction against the sides of ;be chimney, especially if it 
be small, operates powerfully to retard the draught. If the chimney 
be contracted at the bottom, the velocity of the entering air will be 
increased. If it be narrowed at top, the smoke and hot air will be 
discharged above with more force, and hence be less likely to be 
driven down by slight changes in the direction of the wind ; yet con- 
tractions in the diameter of the chimney at any point, diminish the 
total amount of air passing through. In practice, chimney-draughts 
are influenced by several other circumstances, and are frequently so 
interrupted, that they refuse to carry off the products of combustion, 
and are then said to S7nohe. Yet these general statements require 
qualification. A chimney may be so high that the loss of heat through 
its walls shall cool the current down to a point of equilibrium with 
the outer air ; the draught of a high chimney shaft has been greatly 
augmented by enclosing it in an outer case to prevent radiation. Nor 
is the current of air that passes through a chimney, strictly in propor- 
tion to the degree of its heat. The draught, at first, increases very 
rapidly with the temperature, but gradually diminishing, it becomes 
constant between 480° and 570°, beyond which it diminishes, and at 
1800* it is less than at 212°. The reason of this is found in the 
great expansion o." air at a high temperature, by which its volume is 
so much increased, that, although the velocity may be very great, the 
quantity, when reduced to the temperature of the atmosphere, is less 
than at a lower temperature. — "Wtman. 

94. Winds cause Chimneys to Smoke. — A high building, or a tree 
standing close to a chimney and overtopping it, often disturbs its 
draught. The wind passing over these objects, falls down like water 
over a dam, and stops the ascending current so that smoke is forced 
back into the room ; or the wind may strike against the higher object, 
and, rebounding, form eddies, and thus beat down the smoke. "When 
chimneys are not thus commanded by eminences in the vicinity, gusts 
of air may still interfere with their draught. To prevent this, they 



DISTUKBANCES OF THE DRAUGHT. 



51 



are often mounted with turncajys, cowls, or ejectors (354) which are 
so constructed that the effect of the passing wind is to draw off 
the air from the chimney, forming a partial vaciram into wliich the 
gases and smoke rush from helow, and so establish an upward current. 

95. JVew and Damp Chimneys. — When chimneys are new, the brick 
and mortar being damp, are good conductors of heat, and take it 
rapidly from the rising current of warm air. This condenses it, 
obstructs its ascent, and if the fire below be very hot, the chimney 
smokes. As it becomes dry, however, and is gradually covered with 
non-conducting soot, this source of difficulty is removed. 

96. Cold Exposures — Descending Dranghts. — Chimneys in the north 
end of a house, exposed to cold winds, often draw much less perfectly 
than those on other sides, or in the still more favorable warm interior 
of a building. The air in a chimney in the north or shaded side of a 
house is liable to cool in summer, so as to have a dowmmrd, draught, 
when not used. If the temperature of the chimney be nearly the 
same as that of the outer air during the day, the external cooling at 
night may also create a descending current. When, therefore, the 
smoke from the neighboring chimneys passes over the tops of those 
that are drawing downwards, it is sucked in with the current and 
fills the room below. 

97. Currents counteracting each other. — We have seen that it is 
only when the atmosphere is of a perfectly uniform temperature that 
it is perfectly still ; the slightest inequality in its Fig. 13. 
degree of heat, throws it promptly into movement. 
We are apt to forget the exceeding delicacy with 
which the different portions of air are balanced 
against each other. This may be easily shown. 
If two tubes of unequal height be united by a third 
(Fig 13), the candle in the longer tube will over- 
come that in the shorter, and create a downward 
current in the latter ; or if two tubes of equal 
length, imited by a third, as in Fig. 14, have a 
candle in each, one is soon overcome by the other ; 
and this may happen, even when an opening is made in the third 
tube, admitting a limited supply of air. It is sometimes attempted to 
raake a current proceeding from a fire, traverse two flues, which .join 
again before discharging their smoke into the air. But this is 
dilficult, if not impossible ; for though currents may be commenced in 
both routes, one quickly neutralizes the other, and but a single flue 
i& used. 



f 



18 



ACTION AND MANAGEMENT OF CHIMNErS. 



f 10. 14. 



98. One Chimney OTerpowering another. — When 
there are two fire-places in a room, or in rooms 
communicating by open doors, a fire in the one 
may burn very well by itself; but, if we attempt to 
light fires in both, the rooms are filled with smoke. 
The stronger burning fire draws upon the shaft of 
the weaker for a supply of air, and of course brings 
the smoke down with it. This difficulty may be 
remedied by opening a door or window, so as to 
supply both fires with the necessary air. The same 
effect may take place, even though the two rooms 
be separated by a partition, when they communi- 
cate atmospJierically by the joints and doors. Some- 
times, where the windows are tight, a ctrong kitchen fire may over- 
power all the other chimneys in the house and cause them to smoke. 

99. Upper and lower Fines — ^A current entering a chimney through 
a flue horizontally^ may interrupt its draught ; in all cases of flues 
entering chimneys, they should be so arranged that the smoke may 
assume an upward direction corresponding to the course of the main 
current. There is great danger of smoke when the flue of an upper 
room is turned into the chimney of a lower room. If a fire is kindled 
in an upper room when there is none below, the cold air in the main 
shaft rises, and, mixing with the warm an-, dilutes it, and thus checks 
or obstructs the ascent ) while if the lower fire only be kindled, the 
cold air from the upper flue will rush into the shaft, and cooling it 
down at that point, may cause the smoke to descend into both rooms. 
Tlie remedy is, either to keep a fire in both fire-places or to close one 
with a fireboard. 

100. Admission of too mncli Air. — Too large openings in fire-places 
often occasion smoke by admitting so much air from the room as to 
cool the upward current, and thus impair its ascensional force. If 
the fire-place be too high or capacious, or its throat too large, the air 
is drawn from a large space, or it may pass round behind the fire by 
way of the jambs on both sides ; the current is thus impeded, and 
the flame, which should be drawn backward, rises directly against the 
mantel-bar and escapes into the room. The fire-place should be so 
consti'ucted as to compel all the air which enters it, to pass through 
or close to the fire. 

101. Admission of too little Air. — It is well known that a smoky 
chimney is often relieved by opening a window or outer door; where 
this is the case, the diflicidty is a deficiency of air to supply the 



DEFICIENCY OP AIR-SUPPLY. 



59 



draught. Want of a copious and regular supply of air is by far the 
most common cause of smoky chimneys. However Avell coiistructcd 
and arranged may be the flues and fire-places, if they are not supplied 
with a proper amount of air they will inevitably smoke. Of course 
if the room be nearly air-tight, there is no air to supply a current, and 
there will be no current, for as much air as escapes through tho 
ohunney must be constantly furnished from some other source. In 
such a case, the smoke not being carried oflf will diffuse through the 
room. There may even be a double current in the fiq. 15. 
chimney, one upwards from the fire and another from 
the top downwards, as shown in Fig. 15 ; these two 
currents meeting just above the fire, part of the smoke 
is driven into the room. To ascertain the quantity 
needed to be brought in under these circumstances. 
Dr. Feanklin's plan was to set the door open until 
the fire burned properly, then gradually close it until 
again smoke began to appear. He then opened it a 
little wider, until the necessary supply was admitted. 
Suppose now the opening to be half an inch wide, and 
the door 8 feet high, the air-way will be 48 square 
inches, equal to an orifice 6 inches by 8. The intro- 
duction of this air is to be in some way effected, the 
question being where the opening shall be made. It 
has been proposed to cut a crevice in the upper part 
of the window-frame ; and, to prevent the cold air 
from falling down in a cataract upon the heads of the 
inmates, a thin shelf is to be placed below it, sloping 
upwards, which would direct the air toward the ceiling 
of introducing air will be noticed in another place (351). 

102. Draughts through a Room. — Currents of air through a room, 
as from door to door, or window to window, when open, may coun- 
teract the chimney draught ; or a door in the same side of the room 
with the chimney may, when suddenly opened or shut, whisk a cm*- 
rent across the fire-place, to be followed by a puff of smoke into the 
room. 

103. Visible Elements of Smoke. — Smoke consists of all the dust and 
visible particles of tlie fuel which escape unburnt, and which are so 
minute as to be carried upward by ascending currents of air. It is 
chiefly unconsumed carbon in a state of impalpable fineness, which is 
deposited as soot along the flue, or, swept upward by the air current, 
is carried to a greater or lesser height, and finally falls again to tho 




Double current 
in tliimney caus- 
ing smoko. 

The modes 




60 APPARATUS OF WARMING. 

earth. Thus all that is visible of smoke is really heavier than air, 
which may be shown by placing a lighted caudle in the receiver of an 
air-pump. By then exhausting the air, the flame is extinguished ; 
and the stream of smoke that continues to pour from the wick, falls 
Fig. 16. ^^ ^^® pump-plate, as is seen in Fig. 16, because there 
XX is no air to support it. Often, in days when the wea- 

,^-^ ^-"^ ther is said to be ' close' we notice that the smoke 
floats away from the chimney-top and falls instead of 
rising ; so that the air, even within the zone of breath- 
ing, becomes charged with the sooty particles. The 
atmosphere is so rare and light that it cannot sustain 
the heavy smoke. The common impression that the 
air on these occasions is heavy, which prevents smoke 
from rising, is quite erroneous. The visibility of smoke is not entirely 
due to sooty exhalations. "Watery vapor is a large product of com- 
bustion, and, when the air is warm and dry, it remains dissolved and 
invisible ; but, when it is cold or saturated with moisture, it will 
absorb no more, and that which rises from the chimney appears as a 
vapor-cloud, and thus adds greatly to the apparent bulk of the smoke. 

104. Other constituents of SmokCt — Smoke contains many sub- 
stances beside the carbonaceous dust, which vary with the conditions 
of combustion and the kind of fuel used. Coal smoke is alkaline from 
the presence in it of ammoniacal compounds, while wood-smoke is 
acidulous from the ligneous acids it contains. The smarting sensation 
produced by wood-smoke in the eyes, is due to the highly irritating 
and poisonous vaj^or of creosote formed in the burning p~i"ocess. 

XI.— APPARATUS OF WARMING. 

105. The various devices for warming are to be considered in a 
twofold relation, as generating heat and affecting the breathing quali- 
ties of the air. These topics are often treated together ; but, as we 
desire to present the subject of air and breathing with the utmost 
distinctness, a separate part will be assigned to it, and the heating 
contrivances will then be reconsidered in respect of their atmospheric 
influences. 

106. How Rooms lose Heat. — Apartments lose their heat at a rate 
proportional to the excess of their temperature above the external 
air ; the higher the heat, the more rapidly it passes away. Large 
quantities of heat escape through the thin glass windows. The win- 
dow panes both radiate tlie heat outward, and it is conducted away 



SOUKCES OF THE LOSS OF HEAT. 61 

by the external air. Glass is a bad conductor of lieat, yet the jilates 
used are so thin as to oppose but a very sliglit barrier to its escape ; 
on the other hand, it is an excellent absorber and radiator, — so that, 
in fact, it permits the escape of heat almost as readily as plates of iron 
of equal thickness. The loss of heat in winter, by single windows, is 
enormous. Three-fourths or 75 per cent, of the heat which escapes 
through the glass, would be saved by double windows, whether of 
two sashes or of double panes only half an inch apart in the same 
sash. Heat is also lost by leakage of warm rarefied air through 
crevices and imperfect joinings of windows and doors, while cold air 
rushes in to supply its place. Heat also escapes through walls, floors, 
and ceilings, at a rate proportioned to the conducting power of the 
substances of whicli they are composed. Another source of loss is 
from ventilation where that is attended to, whether it be by the chim- 
ney, or through apparatus made on purpose, and it may be estimated 
as about 4 cubic feet of air per minute for each person. This is the 
lowest estimate ; authorities differ upon the point, the ablest putting 
it much liigher (325). The loss from this source is proportional to 
the scale adopted. Much heat, besides, is conveyed away by the cur- 
rents necessary to maintain combustion. To renew the lieat thus 
rapidly lost in these various ways, different arrangements have been 
resorted to, which will now be noticed. 

107. Our Bodies help to Warm the Rooms. — In estimating the sources 
of heat in apartments, we must not overlook that generated in our 
own systems. The heat lost by the body in radiation, is gained to the 
apartment ; in the case of an individual, the amount is small ; but 
where numbers are collected, tlie effect is considerable. In experi- 
ments made upon tliis point, by enclosing different individuals succes- 
sively in a box lined with non-conducting cotton, open above and be- 
low, and suspended in the air, it was found first, that there is a current 
ascending from the person on all sides; and second, that the air was 
found, on an average, 4° liigher «,bove the head than below the feet. 
In a dense crowd, air admitted slowly through the floor at 60°, rises 
to 70° or 80° before reaching the head. The temperature of a lecture 
room 9 feet high, and 34 by 23 square, occupied by 67 persons, and 
the outer air at 32°, rose by the escape of bodily heat during the lec- 
ture, twelve degrees. 

108. Ancicut Method of Warming. — The chimney is a modern device, 
coming into use only 500 or 600 years ago, with the mariner's compass, 
the printing press, mineral coal, and that array of capital inventions 
and discoveries which appeared wltli the raybreak of the new civili- 



62 APPARATUS OF WARMING. 

zatioii that succeeded the dark ages. Previously to that time, housei 
were lieated as Iceland huts are now, — by an open fire iu tlie middle 
of the apartment, the smoke escaping by the door, or passing out 
through apertures in the roof, made for this purpose. The Greeks and 
Komans had advanced no further than this in the domestic manage- 
ment of heat. They kept fires in open pans called iraziers. Tliose 
of the Romans were elegant bronze tripods, supported by carved im- 
ages with a round dish above for the fire. A small vase below con- 
tained perfumes, odorous gums, and aromatic spices, which were used 
to mask the disagreeable odor of the combustive products. The por- 
tion of the walls most exposed were painted black, to prevent the 
visible effects of smoke ; and the rooms occupied in winter had plain 
cornices and no carved work or mouldings, so that the soi)t might be 
easily cleared away. 

1.— OPEN FIRE-PLACES. 

109. Structure and Improvements. — With the chimney came the 
fire-place, which is an opening on one side of its base. At first it was 
an immense recess with square side-walls (jambs) and large enough to 
contain several persons, who were provided with seats inside the 
jambs. These fire-places were enormously wasteful of fuel, and were 
in other respects very imperfect. They have been gradually improved 
in various ways. By reducing their dimensions and greatly contract- 
ing the throat, the force of draught is increased and the liability to 
smoke diminished. By lowering the mantle or breast, the fiow of 
large masses of air which entered the chimney without taking part in 
the combustion, was stopped ; while, by bringing the back of the fire- 
place forward, th e fire was advanced to a more favorable position for 
heating the room. Eays of heat, like those of light, when they strike 
on an object, are reflected at the same angle as that at which they 
fall, — that is, the " angle of incidence is equal to the angle of reflec- 
tion." Now, when the jambs were placed at right angles with the 
back, that is, facing each other, they threw their heat by reflection 
(and when hot by radiation) backward and forward to each other 
across the fire. By arranging the jambs at an angle, they disperse 
the heat through the room. Cotjxt Rumford states that the proper 
angle for the positions of jambs is 135 degrees with the back of the 
fire-place. 

110. How the open Fire-place warms the Room. — The heat of com- 
bustion from the open fire is entirely radiant — thi'own off directly 
from the burning fuel, or reflected from the sides and back of the fire • 



OPEN FIRE-PLACES WASTE HEAT. 



63 



place. It strikes upon tlie walls, ceiling, floor, and furniture of the 
room ; a portion of it is reflected in various directions, and the rest is 
absorbed. The objects which receive it are warmed, and gradually 
impart their heat to the air in contact with them ; — gentle currents 
are thus produced, which help to equalize the temperature of the 
room. Those portions of the air which are in contact with the fire, 
become heated by conduction, but they immediately rise into the 
chimney, and are, therefore, of no use in heating the room. As a fire- 
place is situated at the side of the apartment, and as radiant heat 
passing from its source decreases rapidly in intensity (23), it is 
obvious that the room will be very unequally heated. Near the fire 
it will be hot, while the remote places wiU be in the opposite condi- 
tion. There is a semicircular line around the fire-place, in which 
persons must sit to be comfortable, within which :ine they are too 
hot, and beyond which they are too cold. Of course, in this method of 
warming, the body receives the excess of heat only upon one side at once. 

111. Tlic open Fire not Economical. —Fuel gives out its heat in 

two ways, by radiation and by immediate contact. Peolet has shown, 
by ingenious experiments, that the radiated heat from wood was ^ ; 
from charcoal and hard coal about 5, of the whole amount produced. 
As a general result, those combustibles which burnt with the least 
flame yielded the most radiant heat. As the radiant heat is thus the 
smaller quantity, the arrangements in which it alone 
is employed are by no means economical ; yet the open 
fire-place heats entirely by radiation, and is therefore 
the most wasteful of all the arrangements for heating. 
It is said that in the earlier fire-places 7-8ths, and 
EuMTORD says 15-1 6ths of all the heat generated^ 
ascended the chimney and was lost. It is probable 
that in the best constructed fire-place, from 1-2 to 
3-4tbs of all the heat is thus wasted. The fire-place 
is greatly improved in economy and heating efficiency 
by so constructing it that it may supply a current of 
heated air to the room. This is done in numerous 
ways, as by setting up a soap-stone fii e-place within 
the ordinary one, and leaving a vacant space between 
them, into which cold air is admitted from without, 
which is then thrown into the room through an open- 
ing or register above. This is an excellent plan ; it is 
executed with various modifications, but, if well done, 
it answers admirably. Even a flue made of some thin 



Fig 17 




Air from with- 
out warmed by th<i 
fire-place. 



64 APPARATUS OF WARMING. 

materiiil, and contaiued in the chimney, the lower extremity com 
municating with the external air, and the upper with the room 
(Fig. 17), answers a most useful purpose. Heat is saved; abundance 
of air is furnished to the room without unpleasant draughts, while a 
common cause of smoke is avoided (101). 

112. Franklin Stove. — Dr. Feanklin contrived a heating apparatus 
of cast iron, which he called the Pennsylvania fire-place^ but which 
is generall}' known as the FranMin stove. It offers one of the best 
methods of managing an open fire. It is set up within the room, and 
the hot air and smoke from the fuel, instead of escaping from the fire 
directly up the chimney, is made to traverse a narrow ani circuitous 
smoke flue, which gives out its heat like a stove-pipe ; at the same 
time air is introduced from out of doors through air-passages which 
surround and intersect the smoke-flue, and, after being warmed, it is 
discharged into the room by means of proper openings. This appa- 
ratus warms, not only by radiation from the burning fuel like the 
common fire-place, but also by radiation from the hot iron ; besides, 
the air of the room is heated by contact with the metallic plates, and 
there is still another source of warmth in the hot air brought in from 
without. 

113. Coal Grates. — As coal contains more combustible matter in 
the same space than wood, and produces a more intense heat, a much 
smallei" fire-place answers for it. A very narrow throat in the chim- 
ney is suflicient to carry off the smoke. The coal-grate is a more 
economical contrivance for warming than the larger wood fire-place, 
chiefly because it lessens the current of air which enters the flue. In 
the wood fire-place a copious stream of warm air passes up the chim- 
ney, which takes no part in combustion, but carries oft' with it much 
heat, the place of the escaping warm air being supplied by cold air 
from without. The coal-grate is closed, like the fire-place, on three 
sides, the front consisting of metallic bars or grates, which, while they 
confine the coal, suffer the heat to radiate between them into the 
room. The sides and back of the grate should be formed of fire-brick, 
soap-stone, or some slowly-conducting substance, and not of iron, 
vrhich conducts away the heat so fast as to deaden the combustion — 
for a fire may be effectually extinguished by contact of a good con- 
ducting solid body. For this reason, as Kumfoed first pointed out, 
there should be as little metal about a grate as possible, the bars 
being made as slender and as wide apart as practicable, so as to inter- 
cept the fewest radiations from the burning surface. 

114. Conditions of Combustion in the Grate. — The form of the grata 



COMBUSTION IN GRATES. 65 

sliould be such as to expose the largest surface of ineandescont coal to 
the apartment. If it has a circular front, there will be not only more 
surface, but the heat may then be radiated in all dii-ections ; yet, if too 
great a surface is exposed to air, in extreme cold weather it carries 
off the heat faster than combustion renews it ; and the coal, if it bo 
anthracite, grows black upon the exposed side and burns feebly. The 
art of burning fuel to the best advantage in open grates, is to mahi- 
tain the whole mass in a state of bright incandescence, by preventing 
all unnecessary obstruction of heat, either by contact of surrounding 
metal, or currents of cold air flowing over the fire. It is very difficult, 
however, to expose a large fire-surface to the atmosphere, and at the 
same time properly regulate the quantity of air admitted. It is pos- 
sible for fuel to smoulder away and entirely disappear with the pro- 
duction of very little sensible heat. To be burned with economy, 
therefore, it must be burned rapidly under the most favorable condi- 
tions of vivid combustion. The heat absorbed by the fuel, the sur- 
rounding solids, or the rising vapor, is of course not available, but 
only the excess which is emitted into the room. To cause this lively 
and perfect combustion, all the air which comes in contact with the 
fuel must be decomposed and i>art with the wliole of its oxygen. 
Every particle of air passing up through the fire, which does not help 
the combustion, hinders it, first by cari-ying off a portion of the heat, 
and second by cooling the ignited surface so that it attracts the oxygen 
Avith less vehemence, and thus causes the fire to languish. The air 
should also be pure, that is, as little as possible mingled with the 
gaseous products of combustion. Air entering below a fire, rapidly 
loses its oxygen and becomes contaminated with carbonic acid ; both 
changes unfitting it for carrying on the pi'ocess actively in the upper 
regions of the fire. If, therefore, the mass of burning material is too 
deep, the upper portions burn feebly and at least advantage ; yet if 
the pieces of coal be large, scarcely any depth of fuel wiU be suflicicnt 
to intercept and decompose the cold air which rises through the Avide 
spaces. If the coal be not large, perhaps a depth of four or five 
inches will be found most economical. 

115. Different kinds of Grate— The modifications and variations of 
the fire-place and coal-grate are innumerable : and the multiplied de- 
vices which are continually pressed upon public attention, are, many 
of them, but reproductions of old plans. The use of a simple iron jilate 
for a fire-back, has been employed to warm an adjoining room situated 
behind the fire-place. For the same purpose grates have been hung 
upon pivots, so as to revolve, and thus warm two rooms, as library 



66 APPARATUS OF WAKMING. 

and bedroom alternately. In Golson's stove-gi-ate, the fire is contained 
in an urn or vase-shaped grating, and is surrounded by a circular re- 
flector which throws the rays, both of heat and light, into the room in 
parallel lines. Coal-grates are also constructed on the principle of the 
double fire-place, by which warmed air is introduced into the room from 
without. Dr, Feankliit devised an ingenious grate called the circular 
fire-cage. It was so hung as to allow it to revolve. The coal was 
ignited, as usual, at the bottom, and when the combustion was well 
advanced, the cage was turned over so as to bring the fire at the top 
By this means, the fresh coals at the bottom were gradually ignited, 
and tlieir smoTce having to pass through the fire above them, was en- 
tirely consumed. 

116. Arnott's new Grate. — Dr. Arnott has recently constructed a 
new grate, in which the same benefit — the consumption of smoke, is 
secured. The bottom of the grate is a movable piston, which may be 
made to fall a considerable distance below the lower grate bar. A 
large charge of coals is then introduced, which rests upon the piston 
and fills the grate. They are lighted at the top, so that the heat passes 
downward and consumes the smoke as it is formed below. As the 
coals waste away at the top, the piston may be raised by the poker 
used as a bar, and thus fresh coal is supplied to the fire from teneath. 
When the fii'st charge is consumed and the piston is raised to the bot- 
tom of the grate, a broad, flat shovel is pushed in upon the piston 
which supports the burning coals, and affords a temporary support for 
the fire. The piston is then let down to the bottom of the box, and a 
new charge of coal shot in. This arrangement is valuable for abating 
the smoke nuisance M'here bituminous coal is burned. Much inge- 
nuity has been spent upon contrivances to burn or consume smoke. 
The thing however is impracticable. When smoke is once produced 
by fire, we can no more advantageously convert it to heating purposes 
than we can the smoke of a badly burning candle to the purposes of 
lighting. When smoke escapes from the ill-adjusted flame of a lamp, 
we notice that the flame itself is dull and murky, with diminished light; 
but if it burn without smoke, the flame is white and clear. But we 
do not say in this case, the lamp T)urns its smoTce., but that it turn* 
without smoTce. The aim should be, so to conduct the first combustion 
that smoke sliall be prevented. 

117. Grates should not be set too low,— As the open fire warms by 
radiation, it should be so placed as to favor this mode of diffusing heat. 
The tendency of currents of heated air to rise, secures suflBciently the 
warmth of the upper portion of the room, so that the main object of 



EFFECT OF TOO LOW FIRES, 



67 



FiQ. 18. 



the grate should be to heat the floor. If the fire is situated very low, 
the radiation Avill be considerable upon the hearth, while but few heat- 
rays will strike further back upon the floor. They will pass nearly 
parallel along the carpet or floor, just as the solar rays, at sunrise, 
dart along the surface of the earth. If, however, the fire be raised, 
its downward radiations strike upon the floor and carpet at some dis- 
tance back, with sufiicient force to warm them, just as the sun's rays 
are more powerful when he shines from a considerable distance above 
the horizon. If a in (fig. 18), represent a radiating point or fire in a 
room, and h c the floor, it will be seen 
that no heat-rays fall upon it ; while 
if the floor be at d e, it will receive 
rays from the fire. " In such arrange- 
ment it is seen by where the ray-lines 
intersect this floor, that much of the 
heat of the fire must spread over it, 
and chiefly between the middle of the 
room and the grate, where the feet of al 
the persons forming the fireside cir- 
cle are placed. Striking proof of the "^^ 
facts here set forth, is obtained by 

laying thermometers on the floors of rooms with low fires, and with 
Bimilar rooms with fires as usual of old, at a height of about 15 or 16 
inches above the hearths. The temperature in the upper parts of all 
these being the same, the carpets in the rooms with low fires are colder 
by several degrees than in the others." 




2.— STOVES. 

118. How Rooms are warmed by Stoves.— The stove is an enclosure, 
with us, commonly of iron, so tightly constructed as to admit through 
an aperture or damper, only sufl5cient air to maintain the combustion 
of the fuel, Avhich may be either wood or coal. The heat generated 
within is communicated, first to the metal, and then by that to the 
apartment. It is usually situated quite within the room, the products 
of burning being conveyed away by a flue or pipe. The stove imparts 
its heat by radiation in all directions ; it also heats the air in contact 
with it, which immediately rises to the upper part of the room, that 
which is cooler taking its place in the same manner as heat is dis- 
tributed througli water in boiling (46). 

119, Brick, Earthenware, and Porcelain Stoves.— Stoves made of these 



68 APPAKATUS OF WAEMING. 

materials are most common in Germany and Eussia. They are gen- 
erally made to project into the room from one side, like a chest of 
drawers or a sideboard ; the door for the fire being sometimes in an 
adjoining apartment. These stoves heat more slowly, and conso- 
qnently give out their warmth for a longer time than those made of 
iron, which are subject to rapid variations of temperature. 

120. Self-regulating Stoves. — These are stoves to which are appended 
contrivances for regulating the draught. The principle employed is 
the" expansion of bodies by heat, and their contraction by cold. A 
bar of brass or copper is so attached to the stove, that when the heat 
within increases, it lengthens ; it then moves a lever and closes the 
aperture which admits the draught. This checks the fire, and causes 
the bar slowly to cool ; it now contracts, and again opens the aper- 
ture of draught. Dr. Arnott produced the same result by means of 
a column of air contained within a tube acting upon mercury which 
moved a valve, and thus controlled the air-aperture. As the addition 
and subtraction of heat cause gases to change their bulk m ore readily 
than solids, a well constructed regulator of this kind would be more 
sensitive and prompt in action than one of metal. 

121. Air-tight Stoves. — The so called air-tight stoves are very 
common. They are designed to admit the air in small and regulated 
quantities, so as to produce a slow and protracted combustion. This 
mode of generating heat is less economical than is generally supposed. 
To become most perfectly available, heat must bo set free at certain 
rates of speed. The compounds formed by combustion at a low tem- 
perature, generate much less heat than those which result from quick 
burning. Indeed, in the low, smothered combustion, the fuel under- 
goes a kind of dry distillation, producing carburetted hydrogen gases 
which escape into the chimney ^s unburnt volatile fuel, and are of 
course lost. These gases are inflammable, and when mixed with air, 
often cause explosions in air-tight stoves. Dr. Uee found that 
while 3.V poimds of coke evaporated 4^ pounds of water, from a cop- 
per pan, when burned in a single hour, yet that when the same 
amount was burned in twelve hours, but little over half that quantity 
of water was evaporated. As has been previously stated, to evolve 
the largest amount of heat from fuel it must bo burned rapidly, and 
with a supply of air sufficient to oarry the oxidation at once to its 
highest point, by the production of carbonic acid and water. Where 
the fuel is quickly and completely burned, and the hot, escaping gases 
are made to traverse a sufficient length of pipe to have parted with 
nearly all their heat before entering the chimney, there remains noth- 



POINTS SECUEED BY TUE BEST STOVES. 09 

ing to be desired on the score of economy. It is evident that all the 
heat has been retained in the room, and in this case the stove becomes 
the most efficient heating apparatus. 

122. Eflfect of Elbows iu Stovepipes. — The heating action of the sheet- 
iron flue or stovepipe, is derived from the hot current of air within it. 
In proportion therefore as it contributes to the warmth of the room, 
this current of escaping air is cooled. That this cooling of air within 
the pipe takes place rapidly, may be shown by the ditference of tem- 
perature at its connection with the stove, and where it enters the 
chimney. The cooling takes place of course from without inwards ; 
the outer stratum of the hot air current which is in contact with the 
pipe cools faster than the interior portion, so that the centre of the 
current is the hottest. Now it is well known that the eflfect of elbow- 
joints in a pipe, is to make the same length of it much more efficacious 
in warming a room, than it would be if straight. The cause of this is, 
that the heated air, in making abrupt turns, strikes against the sides 
with sufficient force to break up and invert its previous arrangement, 
and so mingle it, that the hotter air from the interior of the current 
is brought more into contact with the sides of the pipe, and more heat 
is thus imparted. It also checks the rapidity of the current. As radi- 
ation proceeds much slower at low temperatures than at liigh ones, 
the pipe, as it recedes from the stove, becomes rapidly less and less 
useful as a means of diff'using heat into the apartment ; it gives out 
less heat, in proportion to what it contains, than the hotter parts of the 
pipe. There will, therefore, be little gained by greatly lengthening it. 

123. Best qualities of a Stove. — The desirable points to be secured in 
the construction and management of stoves, are, first, ready contriv- 
ances for regulating the draught; second, accurate fitting in the joinings, 
doors, dampers, and valves, to prevent the leakage of foul gases into 
the room ; third, enclosure of the fire-space, with slow conductors, as 
fire-brick or stone ; fourth, a high temperature, attained by the rapid 
and perfect combustion of the fuel ; and fijth, to bring all the heated 
products of the combustion in contact with the largest p)ossil)le alsorh- 
ing and radiating metallic surface, so that the iron in contact with 
the air may not be overheated, but give out its warmth at a low 
temperature. Large stoves, moderately heated, are therefore most 
desirable. The cooler the surface of the stove, or the nearer it is in 
temperature to the air of the room, the more agreeable an(l salubrious 
will be its influence. This desirable result is to be obtained only by 
exposing the greatest quantity of heating surface to the least quantity 
of fuel — a condition almost reversed in our modern stoves. 



70 



APPARATUS OF WARMING. 



S. HOT-AIR ARRANGEMENTS. 

124. Hot-air Farnaccs. — Heating by hot air, as it is termed, lias re 
cently come into very general use. In this case the heater is not situ- 
ated in the apartments to be warmed ; hot air being conveyed from it 
through air-flues to the rooms (fig. 19). The most common plan is a 

hot-air furnace. It is construct- 
'°-' ■ ed of iron, and usually lined with 

fire-brick for burning anthracite, 
and has a flue connecting it with 
the chimney, to remove smoke. 
It is enclosed in a case of iron or 
brick-work, with an interval of 
space between, forming an air- 
chamber. Air is introduced into 
this chamber, either directly 
from the room, or by means 
of a conduit, from without 
the building. The furnace is 
situated in the cellar or base- 
ment, and the entering air heat- 
ed to the required temperature, 
by contact with the hot iron, 
escapes upward from the air- 
chamber through tin tubes, 
which distribute it to all parts 
of the dwelling. It enters the 
room through apertures called 
registers, which may be opened 
or closed at pleasure. This 
method is commended by its 
economy of space, the heating 
machine being excluded from 
the occupied apartments ; fuel 
is also consumed more completely, and with better economy, in a 
single furnace, than if burned in several stoves or grates. A disad- 
vantage however, is, that the power of the furnace being gauged by 
the requirements of a certain sized building, or number of apartmeuti;, 
it is not easily accommodated to a fluctuating demand for heat. 

125. Diffasion of Hot Air throngh the Apartmsut. — There are serioua 




Manner of warming by IIot-Air Furnaces. 



DISTRIBUTION OF HEAT IN THE AIR OF ROOMS. 71 

disadvantages attending the entrance of hot air in large streams 
through registers in the floor. If it be very hot, it will ascend directly 
to the ceiling, without imparting its heat to bodies around. In a 
church, heated by two large hot-air stoves, delivering the air through 
two large openings in the floor, we have found a difference, after the 
heating process has been going on three hours, of more than 20° be- 
tween the temperature near the ceiling and that of the floor. In some 
public buildings, a stratum of air has been observed at the height of 
20 or 30 feet from the floor, with a temperature above that of boihng 
water, while below it has been disagreeably cool. In private houses, 
with the hot-air furnaces, now in general use, air is usually introduced 
at a high temperature. It rises directly to the ceiling, spreads out 
upon it, and on reaching the walls, descends by them and the windows, 
more rapidly by the latter (337), until it reaches the floor, along which 
it is diffused toward the register, when a part is again drawn into the 
ascending current. Hence wo see that those assembling just around 
the register, and not over it, are in the coldest part of the room. 
That this is the case, we have also proved by the thermometer ; while 
the air, midway between the floor and ceiUng, in a moderate-sized 
sitting-room, was at 74°, that near the register, was but 68°. — (Wy- 
MAN.) Even in a room heated by a stove, or any other apparatus 
placed within it, and upon the floor, the air is found, after a time, to 
arrange itself in horizontal layers, the temperatures of which decrease 
from above downwards. In an experiment to ascertain the temper- 
ature in a room 21 feet high, the following indications were obtained. 

Level of floor, 65" 10. 5 80' 

2. 1 foot, 67° 12. 6 Sr 

4. 2 " TO' 14. 7 86- 

6. 3 " 72* 16. 8 90° 

8. 4 " 75* 19 94* 

12G. How we are warmed in Hot-air Rooms. — "We are to remember 
that after all, it is loss the contact of heated air which warms us in hot- 
air apartments, than other agencies. "We may enter a room in whicli 
the atmosphere is at 70°, or even higher, and yet be chilly. Great 
amounts of air contain but little heat. The quantity of heat that will 
raise 1 cubic foot of water 1 degree, Avould be so difi'used as to raise 2,850 
cubic feet of air one degree. — (Aenott.) From the amount of air that 
comes in contact with our bodies, therefore, we cannot get sufficient 
heat to Avarm us rapidly. If the walls, floors, and furniture of the 
room are cold, though the air be warm, the individual radiates heat 
to them, and is compensated by none in return; while if they are 



72 



APPARATUS OF WARMING. 



"warm, they become constant sources of radiant warmth. Hot air may 
also become a direct source of cold if it be dry. If we moisten the 
bulb of a thermometer, and expose it to the rays of a fire, it receives 
the heat and rises ; but when moistened and exposed to the action of 
warm, dry air, it will sink down several degrees, caused by the evap- 
oration which carries off heat. In the same manner, over-dry air may 
promote cooling by increasing bodily evaporation. We shall refer to 
the effects of hot air again. 

127. Heating by Hot Water. — We have seen how water is put in 
motion by lieat ; the accompanying figure shows the working of the 

Fig. 20. principle. As the lamp heats the water on one side 

of the tube, it expands and ascends, the colder 
water coming forward from below to take its place, 
which establishes a circulation. As the hot water 
passes round the circuit, it gradually parts with its 
heat through the tube to the surrounding air. The 
great specific heat of water (49) by which it holds a 
large quantity of caloric, adapts it well for the 
transportation of this agent ; and, as it parts with 
its large portion of heat but slowly, it is the most 
constant and equable of all sources of warmth. We 
have already referred to the significant fact that 
when the heat of a cubic foot of Avater is imparted 
to air, whatever be the number of degrees through 
which the water falls, it will raise through the 
same number of degrees 2,850 cubic feet of air. 

128. Two forms of Hot Water apparatus. — There are two methods of 
warming houses by hot water. In one the mechanism is placed in 
the cellar or basement, and heats air which is conveyed upward to 
warm the apartments above, as in the case of furnaces. In this form 
of the mechanism, the pipes do not ascend to any considerable height 
above the boiler ; but, in the other plan, a system of small tubes is 
distributed through the house, being laid along to fit any form and 
succession of rooms and passages, or they are coiled into heaps in 
various situations, and impart their heat by direct radiation. There 
is a difference in the degree of heat in these two plans. Water 
exposed to fire, as we have seen, rises in temperature to the boiling 
point and goes no higher, but this varies with depth and pressure. 
In those arrangements, therefore, which are confined below, the water 
hardly rises above the temperature of 212° ; while, in those which 
extend through the dwelling, it ascends many degrees higher. A 




Circulation of water. 



STEAM-HEAT DANGEK OF FIKE. 73 

good hot-water arrangement, from its constancy and regularity of 
action, and when not heated above 200° or 212°, affords one of the 
most agreeable modes of heating a dwelling, although it is at present 
60 expensive as to place it beyond popular reach. 

129. Steam Apparatas for WarmiBg. — As steam contains a large 
amount of heat (68), it becomes an available means of its transmission. 
If admitted into any vessel not so hot as itself, it is rapidly condensed, 
and at the same time gives its heat to the vessel, which may then 
diffuse it in the space around. A system of tubes ascending from a 
boiler may be so arranged as to warm the air which is thrown into 
the room through a register, or they may be wound into coils as in 
the previous case (128), and dispense their heat by radiation. The 
pipes are so placed, that the water from the condensed steam flows 
back to the boiler, or the hot water may be drawn off into vessels 
which are made to contribute to the heating effect. This mode of 
heating requires a temperature always at 212° for the formation of 
steam, and often much higher to drive forward the condensed water 
and clear the pipes. A serious drawback to this mode of heating is 
that the apparatus often emits a disagreeable rattling or clacking 
sound, owing to the condensation within the pipes and the sudden 
movements of steam and water. There is also a fundamental objec- 
tion to the method of warming rooms by heat radiated from coils of 
pipes, whether they be heated by steam or hot water. In respect of 
the condition of the air, this is liie worst of all methods of heating, 
for it makes no provision whatever for exchange of air. All the 
other heating arrangements involve more or less necessary ventilation, 
but radiating pipes afford none at all. 

130. Risk of Fire by these methods of Warming.— It has been supposed 
that the employment of hot water, hot air, and steam pipes, as a 
means of heating buildings, cuts off the common sources of danger 
from fires, and is entirely safe. This is a serious error. Iron pipes 
liable to be heated to 400°, are often placed in close contact with 
floors skirting boards and wooden supports, which a much lower 
degree of heat may suflice to ignite. By the long-continued applica- 
tion of heat, not much above that of boiling water, wood becomes so 
baked and charred that it may take fire without the applicatioa of a 
light. A considerable time may be required to produce this change, 
60 that a fire may actually be " Tclndling vpon a man's, premises for 
years.'''' The circular rim supporting a still which was used in the 
preparation of some medicament that requu-ed a temperature of only 
300°, was found to have charred a circle at least a quarter of an inch 

4 



74 APPAEATUS OF WARMING. 

deep in the wood beneath it in less than six months. There are nu- 
merous cases of buildings fired by these forms of heating apparatus. 

131. Origin of Fires. — The Secretary of a London Fire Insurance 
office stated that the introduction of lucifer matches caused them an 
annual loss of $50,000, Of 127 fires caused by matches, 80 were 
produced by their going off" from heat ; children playing with them, 
45 ; rat gnawing matches, 1 ; jackdaw playing with' them, 1. "Wax 
matches are run away with by rats and mice, taken into their holes 
and ignited by gnawing. These facts point to the indispensableness 
of match-safes. In London, during a period of nine years, the pro- 
portion of fires regularly increased from 1.96, at 9 o'clock, A. M, the 
time at which all households might be considered to be about, to 3.44 
at 1 o'clock, P. M ; 3.55 at 5 P. K, and 8.15 at 10 P. M., which is just 
at the time that fires are left to themselves. 

132. Benefits and Drawbacks of the Tarions methods of Heating. — Each 
plan of warming presents its special claims to attention, and vaunts its 
peculiar benefits. Modifications of every scheme are numerous, and 
still multiplying. As a result of this inventive activity, there is a 
gradual but certain improvement. The aim of inventors has hitherto 
been mainly to secure economical results ; a laudable purpose, if not 
pursued at the sacrifice of health. As people generally become 
better informed respecting the principles and laws which influence the 
comfort and well-being of daily life, improvements wiU be demanded 
in this direction also. Meantime, each method is to bo accepted with 
its imperfections, though we are not to forget that in their working 
results much must depend upon proper and judicious management. 
We recapitulate and contrast the chief advantages and disadvantages 
of the various methods of heating. Some of the points referred to, 
particularly those which relate to ventilation, have not been previ- 
ously noticed, and will be considered when speaking of air. 

ADVANTAGES OF OPEN FIUE-PLACES. DISADVANTAGES OF OPEN FIRE-PLACES. 

They promote ventilation — afford a They are uncleanly — require frequent 

heerful fireside influence — warm objects, attention — are not economical — are apt to 

without disturbing the condition of the air strain the eyes — heat apartments unequally 

— and may furnish warm air from without. — are liable to smoke. 

ADVANTAGES OF STOVES. DISADVANTAGES OF STOVES. 

They cost but little — are portable— are They afford no ventilation — if not of 

quickly heated — and consume fuel eco- heavy metal-plates, they quickly lose their 
ttomically heat — yield fluctuating temperatures — are 

liable to overheat the air — are liable to 
leakage of gases— and are not cleanly. 



HOT-WATEE APPAEATUS. 



^5 



ADVANTAGES OF HOT-AIR 
FURNACES. 

They are out of the way and save space 
— are cleanly — give but little trouble — may 
afford abundant ventilation — need waste 
Dut little heat — and warm the whole house. 



DISADVANTAGES OF HOT-AIR 
FURNACES. 
They are liable to scorch the air— cannot 
be easily adapted to heat more or less space 
— are liable to leakage of foul gases— and 
they dry and parch the air if copious moist- 
ure is not supplied. 



ADVANTAGES OF HOT-WATER 
APPARATUS. 

They do not burn or scorch the air — 
give excellent ventilation — do not waste 
heat — and they warm the whole house. 
These remarks do not apply to those which 
heat rooms by radiation from coils of pip© 
(129). 



DISADVANTAGES OF HOT-WATER 
APPARATUS. 

They aro expensive in first cost — if 
adapted for an average range of tempera- 
ture, they may fail in extreme cold weather 
(as may also furnaces) — and may give a dry 
and parched air if moisture be not supplied. 



PART SECOND 

LIGHT. 



I. NATUKE OF LIGHT— LAW OF ITS DIFFUSION. 

182. How the outward and inward Worlds Commnnicate. — We sit at 

the window, and have report of the world without. That intelligent 
consciousness which has residence in the chambers of the brain, holds 
intimate communion with the external universe, by means of a com- 
pound system of telegraphing and daguerreotyping, as much superior 
in perfection to the devices of art, as the works of the Most High 
transcend the achievements of man. "We lift the curtains of vision, 
and a thousand objects, at a thousand distances, of numberless forms 
and clad in all the colors of beauty, are instantaneously signalled to 
the conscious agent within. Each point of all visible surfaces darts 
tidings of its existence and place, so that millions upon millions of de- 
spatches which no man can number, enter the eye each moment. A 
landscape of many square leagues sends the mysterious emanation, 
which, entering the camera-box of the eye, daguerreotypes itself upon 
the retina with the fidelity of the Infinite. Fresh chemicals are 
brought every instant, by the little arteries, to preserve the sensitive- 
ness of the nerve-plate, while those that have been used and spent, 
are promptly conveyed away by the veins. As impressions are thus 
continuously formed, they are transmitted, perhaps by a true electric 
agency, along the line of the optic nerve, to be registered in the brain, 
and placed in charge of memory. By the magic play of these 
wonderful agents and mechanisms, the world without is translated 
within, and the thinking and knowing faculty is brought, as it were, 
into immediate contact with the boundless universe. Let us inquire 
farther then, into the nature and properties of this luminous principle, 
and how Ave are related to, and aflfected by it. 

133. Exhilarating Agency of Light. — Light is a stimulus to the ner- 
vous system, and through that, exerts an influence in awakening and 



OLDER NOTIONS OF ITS NATURE, 11 

quickening the mind. Tho nerves of sense, the brain and intel- 
lect, liave their periods of repose and action. The withdrawal of 
light from the theatre of effort is the most favorable condition, as well 
as the general signal, for rest ; while its reappearance stirs us again 
to activity. There is something in darkness soothing, depressing, 
quieting ; while light, on the contrary, excites and arouses. It is com- 
mon to see this illustrated socially ; — a company assembled in an apart- 
ment dimly lighted, will be dull, somnolent and stupid ; but let the 
room be brightly illuminated, and the spirits rise, thought is enlivened, 
and conversation proceeds with increased animation. " Most delicate 
and mysterious is the relation which our bodies bear to the passing 
light! How our feelings, and even our appearance change with every 
change of the sky I When the sun shines, the blood flows freely, and 
the spirits are light and buoyant. When gloom overspreacs the heav- 
ens, dulness and sober thoughts possess the mind. The energy is 
greater, the body is actually stronger, in the bright light of day, while 
the health is manifestly promoted, digestion hastened, and the color 
made to play on the cheek, when the rays of sunshine are allowed 
freely to sport around us." 

134. Ancient Conceptions of Light. — Light is that agent which reveals 
the external world to the sense of sight. The ancients believed it to 
be something born with us — an attribute or appendage of the eye. 
They thought that the rays of light were set into the organ of vision, 
and reached or extended away from it, so that we see in the same man- 
ner as a cat feels by the whiskers which grow upon its face, — ^by a 
kind of touching or feeling process. 

135. Newton's View of its Nature. — ^Modern science regards light as 
an agent, or force, originating in luminous bodies, and flowing away 
from them constantly and with great rapidity, in all directions. But 
how ? The human mind is never satisfied with the mere appearances 
of things. It demands a deeper insight into their nature, — an explana- 
tion of their causes. The first scientific attempt to explain the nature 
of light, and the cause of vision, likened the sense of sight to that 
of smell. We know that to excite the sensation of smell, material 
particles, emanating from the odorous body, pass through the air and 
are brought into contact with the olfactory nerve of the nose. It was 
supposed that light aflTects the eye as odors do the nose ; that it con- 
sists of particles of amazing minuteness, which are shot from the lu- 
minous source, and entering the eye, strike directly upon the optic 
nerve, and thus awaken vision. This was the view of Newton, but 
It is now considered untenable and is generally rejected. It is at pres- 



Y8 



HOAV LIGHT IS DIFFUSED. 



ent thought that light is motion rather than matter, and that tlie eye 
is influenced by a mode of action resembling that of the ear rather 
than that of the nose. "We omit further reference to this question 
here, as the analogy will be mure fully traced when we come to speak 
of colors (150). 

136. Light loses Intensity as it is Diffused. — The rays of light proceed- 
ing from any source, a candle for example, spread out or diverge, as we 
notice nightly. As hght thus diffuses from its source, the same quan- 
tity occupies more and more space, and it becomes rapidly weaker or 
less intense. This takes place at a regular rate. Its power rJecreases 
from each point of emission, in the same proportion that the space 
through which it is diffused increases, exactly as occurs in the case of 
radiant heat ; and this is as the square of the distance. The light 
which at one foot from a candle occupies a given space, and has a 
given intensity, at two feet is diffused through four times the space, 
and has but one fourth the intensity ; at three feet it spreads through 
nine times the space, and therefore has but one-ninth the intensity ; 
following the law of radiant heat, as is shown in Fig. 21. If we are 
reading at a distance of three feet from a lamp, by removing the book 
one foot nearer to it, more than double the quantity of light will fall 

^*®' 21- upon the page ; and if we carry 

it a foot closer, we shall have 
nine times the amount of light 
to read by that we did at fir?t. 
This effect, however, may be 
modified by the light reflected 
back from the walls, and which 
is always more, the whiter they 
are. Whitewashed walls and 
light-colored paper economize 
light, or give it greater effect 
than dark walls, which absorb or waste it. 

137. How Bodies receive the Lnminoas Principle. — When light falls 
upon various kinds of matter, they behave toward it very differently. 
Some throw it back {reflection) ; some let it pass through them (trans- 
mission) ; some swallow it up or extinguish it (absorption) ; and some, 
as it were, split it to pieces (decomposition). All bodies, according to 
their nature and properties, affect light in one or more of these modes, 
producing that infinite variety of appearances which the universe 
presents to the eye. 






ITS EELATION TO SUKFACES. "79 

II. REFLECTION OF LIGHT. 

138. Those bodies which will not allow the light to pass through 
them, are called opaque. "When the rays of light strike an opaque 
body, a portion of them, according to the quality of the surface, is 
absorbed, and the remainder are thrown back into the medium through 
which they came. This recoil, or return of the rays, is called reflec- 
tion of light. 

139. The Law of Reflected Light.— When a ray of light strikes per- 
pendicularly, or at right angles, upon a reflectmg surface, it is thrown 
back in exactly the same path or line. If a 5, Fig. 22, be a ray of 
light falling perpendicularly upon a reflecting Fig. 22. 
surface, it will be thrown back in the same 
direction & a. But if the ray fall upon such 
a surface in a slanting or oblique manner, it 
glances off or is reflected, at exactly the same 
angle, as shown by the arrows. The angle Refidetimr^ 
of rebound is equal to the angle of striking ; " 

or, as it is commonly said, — the angle of eefleotion is equal to 

THE ANGLE OF INCIDENCE, THE REFLECTED EAT IS ON THE OPPOSITE 
SIDE OF THE PERPENDICTJLAE, AND THE PERPENDICULAR, THE INCIDENT 
AND THE REFLECTED BAYS ARE ALL IN THE SAME PLANE. PlaCe a 

looking-glass upon a table, in a dark room. Let a ray of light, 
entering through a hole in a window shutter, strike upon its re- 
flecting surface, it will be thrown olf at an equal angle, and both the 
incident and reflected rays wUl be made visible by the particles of dast 
floating in the room. 

140. How Reflected Light is scattered, — Parallel rays falling upon a 
plane eurface, are reflected parallel, as shown in Fig. 23 ; but sepa- 
rating rays falling upon such a sm-face are reflected divergently, or 
scattered. The beams of light from a candle Fig. 24 diverge before 
falling upon a mirror ; and as each single ray makes 

the angle of incidence equal to that of reflection, it ^^>;o.^ ///Z^ 
is clear that the rays must continue to diverge when '^iyy-\-y//^<^^ 
they are reflected, as in the dotted lines in the "-y^'-'iY 

figure. Thus when a burning candle is placed before a looking-glass, 
its diverging rays strike the mirror surface, and being reflected in 
divergent lines, are dispersed through the room. 

141. The Image in the Looking-glass. — A highly polished metallic 
surface, called a speculum^ is the most perfect reflector. Mirrors, 
or looking-glasses, consist of glass plates coated with metal. It is 



80 



PEODUCnON OF IMAGES. 



Fig. 24. 




Fia. 25. 



not the glass, in looking-glasses, that reflects the light, but tha 
metallic coating behind it. If we place any illuminated object before 
a plane mirror, rays of light pass from all points of 
its surface, and convey an image of it to the mirror. 
But the polished surface does not retain the image ; 
it reflects or throws it back, so that the eye per- 
ceives it. The light which enters the eye comes 
from the real object, which appears behind the 
glass, because the angle or bend in the ray is not 
recognized. The light from an object may be re- 
flected many times, and make a great number of short 
turns, but it will seem as if the rays came straight 
from the object, and it will always appear in the 
direction in which the last reflection comes to the 
eye. This will cause the image to appear as far 
behind the glass as the object is before it, as 
the accompanying diagram (Fig. 25) shows. A 
perfectly plane surface reflects ob- 
jects in their natural sizes and propor- 
tions ; but if the form of the reflecting 
surface be altered, made hollow {con- 
cave), or rounded {convex), they cause 
the image to appear larger or smaller 
than the objects ; or the image is dis- 
torted in various ways, according to 
the figure of the surface, "We see this 
linaje constantly illustrated in the images of 
the face, formed by the bright metallic 
looking-glass. surfaces of domestic utensils. 

142. A perfect Reflecting Surface would l>e luvisible.— If the surface 
of an opaque body could be perfectly polished, it would perfectly 
reflect all objects placed before it, so that the images would appear as 
bright as the realities; but, in such a case, the reflecting surface 
would be itself invisible, and an observer looking at it could see 
nothing but reflected images. If a large looking-glass, with such a 
surface, were placed at the side of a room, it would look like an 
opening into another room precisely similar, and an observer would 
be prevented from attempting to walk through such an apparent 
opening, by meeting his image as he approached it. If the surfaces 
of all bodies had this property of reflecting light, they would be 
Invisible, and nothing could be seen but the lights, or sources of illumi 




f 



■•^•-, 



Cbfoci 

How the imago appears behind the 



TWO KINDS OF KEFLECTED LIGHT. 81 

nation, and their multiplied images. Upon the earth's surface nothing 
would be visible but tlie reflected images of the sun and stars, and in 
a room, nothing except the spectres of the artificial lights, thrown 
back by one universal looking-glass. But perfect polish is impossible ; 
there are no surfaces which in this manner reflect all the light. 

143. In what maimer Light makes olyccts Visible. — It is by reflected 
light that nearly every object is seen. No surfaces are perfectly flat ; 
they may appear so, but, when closely examined, they are found to 
consist of an infinite number of minute planes, inclined to each other 
at all possible angles, and therefore, receiving and reflecting the light 
in all possible directions. If a ray is let into a dark room, and falls 
upon a bright metallic surface, a brilliant spot of light wiU be seen 
from certain points, but the reflecting surface will be almost invisible 
in other directions, and the room will remain dark. If, now, a sheet 
of white paper be substituted for the mirror, it can be seen in all 
directions, and will slightly illuminate the apartment. The surface 
of the paper scatters the light every way, producing an irregular 
reflection. It is this scattered and difl^ised light which makes the 
surfaces of objects visible. Thus light irregularly reflected exhibits to 
us real objects^ while light regularly reflected discloses only semblances 
and images. We see the image in a looking-glass, by light regularly 
reflected ; we see the surface of the glass itself, by the light scattered 
by the minute inequalities of its surface. This irregularly reflected 
light diverges from each point of every visible surface in all direc- 
tions^ so that the object may be seen from whatever point of view we 
look at it, provided other hght does not interfere (144). It follows 
the law of radiation, that is, it flows from each point as a focus, but 
it does not conform to the principle of regular reflection, which has 
just been noticed. The direction of the reflected rays is independent 
of each of the incident rays. In this manner light is radiated from 
surface to surface, so that in the immediate absence of any original 
luminous fountain, there is a reverberation of light from object to 
object, through an endless series of reflections, so that we have 
general and equal illumination. 

144. Management of Light in hanging Pictnres. — The foregoing prin- 
ciples are variously applicable ; hanging pictures upon the walls ol 
rooms may be taken as an illustration. As it is irregularly reflected 
light that reveals to us the picture, it should be so placed that from 
the most natural point of observation that light reaches the eye, and 
not regularly reflected light. If the light fall upon a picture from a 
window on one side of it, and wo stand upon the other side, as at h (Fig. 

4* 



82 



EELATION OF PICTUEES TO LIGHT. 



Fio. 26. 




Window 



Fig. 2T. 



26), the eye is filled with the glare of the regularly 
reflected light, whUe the picture itself can hardly 
be seen. In such a case, the true position of the 
observer is perpendicular to the plane of the picture, 
as at a in the figure. As pictures are often sus- 
pended higher than the eye, they require to be 
inclined forward, and the degree of their inclination 
should depend upon their height and the distance 
of the point at which they may be best observed. 
They should be inclined until the line of vision is 
perpendicular to the vertical plane of the picture. With the eye at a 
and the picture at 1 (Fig. 27), its proper inclination would be to c ; 

but if it were elevated to <?, it should 
fall forward to e. "We will further re- 
mark that pictures should be placed as 
nearly as possible in the same relation 
to light as when they were painted; 
that is, if the shadows fall to the right, 
the illumination should come from the 
left to produce harmonious effects. 

145. Light scattered by tbe Atmosphere. 
— ^By this kind of irregular reflection, 
the atmosphere diffuses and disperses 
the light, — each particle of air acting as 
a luminous centre, radiates light in every 
direction. If it were not for this, the sun's light would only enter 
those spaces which are directly open to his rays, so that, shining 
through the window of an apartment, that portion only where the 
beams passed would be enlightened, and the rest of the room would 
remain totally dark. This secondary radiation occasions the mild and 
softened light which we experience when the heavens are screened 
with clouds, instead of the intense and often painful glare of a cloud- 
less summer day. In the same manner the atmospheric particles 
scatter the rays and diffuse a subdued illumination at morning and 
evening twilight, while the sun is below the horizon. 




• III.— TRANSMISSION AND REFRACTION OF LIGHT. 

146. When light falls upon transparent objects, as air, water, glass, 
it passes through or is said to be transmitted. Bodies vary greatly 
in this power of passing the light, or transparency. The metals are 
least transparent, or most opaque, yet they are not eutirelv so ; thin 



LIGHT KEFEACTED OR BROKEN. 83 

gold leaf, for example, transmits a greenisli light. Nor are there any 
bodies which transmit all the light ; the most transparent detain or 
absorb a part of it, A considerable portion of the sun's light is ab- 
sorbed in the atmosphere ; it does not reach the earth ; and it has 
been calci;lated that if the atmospheric ocean were 700 miles deep, the 
solar light would not pass through it, and the earth would be in dark- 
ness. The purest water of a depth of seven feet, absorbs one half the 
light which falls upon it, and of 700 feet depth, extinguishes it. 

147. Fracture or Refraction of the Rays. — When light passes from 
one substance to another of a different density, as from air to water, 
it is liable to be turned out of its straight course. If it pass from one 
medium to another in a line perpendicular to its surface, as a & (Fig. 

28), it will not be diverted ; but if it fall at an angle, 
as at c d, it will not continue straight to d, but will be 
as it were broken or refracted and proceed to c. If 
the refracting medium have parallel surfaces, the ray 
on leaving it is again bent back to its original course, 
as is shown in the figure. For this reason common 
window panes, which consist of plates of glass with 
^e parallel surfaces, unless they contain flaws, produce no 
distortion in the appearance of the objects seen through them. "When 
light passes obliquely from a rarer to a denser medium, as from air to 
water, it is turned toward a perpendicular ; when from a denser to a 
rarer medium, as from water or glass to air, it is turned /rem a per- 
pendicular, as shown in Fig. 28. 

148. How Refraction may be shown. — A stick, with half its length 

placed obliquely in water, appears bent at the sm-face ; this is because 

the rays are bent, so that those which come from that portion of the 

stick which is in the water, show it in a false place. Put a coin in 

any opaque dish upon a table, and step back, untU the edge of the 

vessel just hides it from view. Now, if water be carefully poured in, 

without disturbing its position, the coin will become visible (Fig. 29) , 

the rays of light coming from it, which before 
Fig. 20. , , , „ ■, , 

passed above the eyes of the observer, are 

now, as they come into the air, bent down- 
ward /to?/^ the per2:>endicular. Bodies possess 
difierent degrees of refractive power. When 
we look through a mass of water, as in a pond 
or stream, the rays are so altered that it 
appears only three-quarters as deep as it really 
IS. Cases of drowning have happened ihrcnigh ignorance of thL«3 





84 



WAVE THEORY OF LIGHT. 



Fig. 




Plane-convex 
Lens. 



Fro. 82. 




Fig. 31. 



illusion. The degree to which any substance bends the light from ita 

straight course is called its index of refraction. Each transparent. 

body has its refracting index, which is one of the properties by which 

it may be known, 

149. Effect of Lenses npon Light.— This power which bodies have, of 
bending light from its straight course, 
is employed when we desire to gather 
it to a point or focus, or to concentrate 
it ; or when it is wished to disperse and 
diffuse it. Pieces of glass, cut or ground 
into various shapes, are commonly used 
for this purpose, and are called lenses- 
A plane convex lens (Fig. 30), or a 
double convex lens (Fig. 31), collect 
the rays of light; while a plane-con- 
cave lens (Fig. 32), or a double-concave 
lens (Fig. 38), separate them, or spread 
them out into a greater space. Com- 
mon spectacle glasses are examples of 
these forms of lenses (248). 




Double-convex 

Lens. 



Fig. 33. 




Plane-concave 
Lens. 



Double-concave 
Lens. 



IV. THEORY OF LIGHT— WAVE MOVEMENTS IN NATURE. 

150. Light not Matter hat Motion. — Thus far we have considered light 
as if it were simple, without inquiring if it be really so, or compounded 
of different elements. There is another way in which the objects of 
nature receive and dispose of it, which brings us to the question of 
composition, and the subject of color. But what is color ? and what 
is light, in nature and essence ? Or what opinion has been formed of it, 
by those who have thought upon the subject most deeply? In its 
cause and mode of movement, light is believed to resemble sound ; 
it is propagated, not by moving particles of matter, but by impulses 
of motion, which progress unaccompanied by any material substances. 
Let us note how wave-motions take place, and the known extent of 
their occurrence in nature. 

151. Visible Wave Motions in Nature. — If we fasten one end of a cord, 
and holding the other strained tight, move the hand sharply up and 
down, or from side to side, waves will be formed, which proceed along 
the string. The real motion, in this case, is at right angles to the di- 
rection of the string, the apparent motion is forward. The particles 



SOUND PEODUCED BY AIR-WAVES. 85 

composing the cord make excursions right and left, or up and down, 
which gives rise to forward wave-impulses. All have noticed what 
takes place in a field of grain when the wind blows. A succession of 
waves appear to pass over the field ; but it is not the grain tbat moves 
along over the ground ; every stalk keeps its place, and only bows its 
head. Yet wave-motions are seen to flow successively forward. If 
we toss a stone into perfectly still water, the surface will be thrown 
into agitation, and waves will pass rapidly from the point where it 
struck, outward, in all directions. The water in this case does not 
move forward any more than the grain did. This is proved by the 
circumstance that any objects which may be seen floating upon the 
water are not carried along by the advancing waves, but only move 
up and down in their places. Thus, particles of water, moving veHi 
cally, cause wave-motions to travel horizontally. 

152. Sound the result of Waves in the Air. — Air is the medium which 
conveys sound to the ear. If a bell be rung in a vacuum, we cannot 
hear it. The air in some way transmits or conveys the sound from 
point to point. How is it done ? There is no passage of air-particles, 
no current or breeze moving from the sounding body to the ear; the 
atmospheric medium is thrown into vibratory motion, and it is air- 
waves only which move forward. We all know that sonorous bodies 
vibrate when struck, and that sound results. A harp-string, when 
struck by the fingers, swings rapidly backward and forward for a 
certain time, producing a sound as long as the vibration lasts. A 
piece of steel wire, or a pin held between the teeth, utters a sound 
as often as the free end is inflected. By touching the teeth with the 
prongs of an excited tuning-fork, we can feel the vibrations. Sound 
is thus not only motion, but it is vibratory motion, and its transmission 
to the ear is due to the flight of air-waves, which, striking against tbe 
auditory drum, communicate sensations of sound to the brain througl 
the auditory nerve. 

153. Upon what the differences of Sound depend.— If sounds are thus 
caused by vibrations, it would seem that the quality of sound should 
depend upon the quaUty of the vibrations; which is the fact. The 
first distinction among sounds is into high and low, or acute and 
grave ; it is a difference of pitch. Slow vibrations produce grave 
sounds of a low pitch. In the case of strings, for example, the larger 
they are the heavier they are, and the looser they are the slower are 
their vibrations, and the deeper are their sounds; while, on the other 
hand, the shorter, lighter, and tighter they are the quicker are their 
vibrations, and the higher and sharper the sounds they give. Eac)* 



86 WAVE-THEORY OF LIGHT. 

sound, therefore, that can be made, is the result of a certain number 
of air vibrations, and to that pitch of sound always belongs that num- 
ber. Sat ART contrived a machine by vrhich the number of pulsations 
which belong to each tone has been determined by actual experiment. 
A thin plate of metal was struck by each tooth of a revolving cogged 
wheel, the motion of which was easily measured. In this way he de- 
termined the exact number of vibrations in the tones forming the 
usual musical scale. 

154. Harmonic Ratios of the Mnsical Scale.- -It was found, experimen- 
tally, that the orchestra pitch note A, of the treble cleff", is produced 
by 853 vibrations per second. The number of pulsations in each note 
of the octave is as follows : 

Eatio of Haemonio Sounds. 

j~, CPE F G A B I C ( 



"S~ 



S 



£S_ 



No. of Vibrations 512, 576, 640, 682, 768, 853, 960 1024, 

Intervals 64, 64, 42, 86, 85, 107, 64. 



It wiU be seen that in the highest note of this scale there are just 
twice as many vibrations as in the lowest ; the interval which they 
comprise is called an octave. The difference between the number of 
pulsations in any note, and the same note in the octave above, is as 1 to 2. 
Hence, by halving the numbers of any scale we obtain the numerical 
value of the octave below; while by doubling them we have the 
number of vibrations made by the notes in the scale above. The 
lowest note of a seven octave piano is made by 32 vibrations in a sec- 
ond, and the highest by 7,680. Two tones having exactly the same 
number of vibrations are said to be in unison. "When their numbers 
are not the same, but are in some simple relation, a concord is pro- 
duced. If one has twice as many as the other an octave results, which 
is the most pleasing of all concords. The simpler the numerical ratio 
between the vibrations which generate a sound, or the air-waves 
which reach the ear, the more perfect and sweet the concord. When 
the difference is such that the proportion cannot readily be recognized 
by the ear, discord is the result. The whole phenomena of music thus 
resolve themselves into certain harmonious numerical ratios among 
air-waves, by which impressions are produced in a certain exact order, 
apon a mathematically constituted organ — the brain. 



SCALE OF THE LUMINOUS VTBBATIONS. 87 

155. Light and Colors result from Wave Motion. — As all sound and 
music are thus due to measured wave movements in the air, it is 
thought also that light has a similar origin. This view assumes, that 
throughout the universe there exists a subtle, all-pervading and in- 
finitely elastic ether^ and that vision is the result of vibrations or wave 
movements sent through this ether, from the source of light to the 
nerve of the eye ; and as different musical sounds are produced by 
varying rates of vibration in the air, so it is suspected that different 
colors are due to the different rates of vibration in the luminous ether, 
and philosophers have gone so far as even to measure the wave-lengths 
of the different elements of light. By wave-length is meant the dis- 
tance from the top or crest of one wave to that of the next ; and it 
is inferred from certain interesting experiments made by Newton, that 
the length of waves, although exceedingly small, differs in the different 
colors, red being largest and violet smallest. In an inch length of a 
ray of red light there are 37,640 vibrations; in an inch of yellow 
light, 44,000 ; and in an inch of the violet ray, 59,756. Iftheminute- 
.ness of the wave excite surprise, it may be replied that this is by no 
means the strongest illustration of the smaUness of the scale upon 
which nature's works are often constructed. Indeed, in this case it 
has been even outstripped by art. M. Nobeet, of France, has ruled 
lines upon glass, for microscopical test-purposes, but the -^i\qq of an 
inch apart.* 

15o, Albrations per second of the Inminons Ether. — But the demon- 
strations of science carry us into far profounder regions of wonder. 
The speed of light has been measured ; the velocity with which it 
moves is in round numbers 200,000 miles per second. That is, when 
we look at any thing, an agent or force sent from the illuminated body 
streams into the eye at the rate of 200,000 miles in a second. Know- 
ing the rate at which light moves, and the number of waves in an 
incli for any particular color, it is easy to ascertain the number of 
vibrations made by each in a second. In two hundred thousand miles 
there are a thousand mUlions of feet, and, therefore, twelve thousand 
millions of inches. In each of these inches there are forty thousand 
waves of red light. In the whole length of the red ray, therefore, 
there are four hundred and eighty millions of millions of waves. 
Now as this ray enters the eye in one second, and tlie retina 
pulsates once for each of these waves, we arrive at the astonishing 
conclusion, that where we behold a red object the membrane of the 
eye trembles at the rate of forir Imndred and eighty millions of mil- 
lions of times between every two ticks of a common clock. Of yellow 

♦ Sec Appondix iJ. 



88 



COMPOSITION AND MUTUAL nTPLUENCE OF COLORS. 



light five hundred and thirty-five milhons of millions of -waves enter 
the eye, and beat against the nerve of vision in the sixtieth part of a 
minute ; "if a single second of time he divided into a miUion of equal 
parts, a wave of violet light trembles or pulsates in that inconceivably 
short interval seven hundred and twenty-seven millions of times." 
Vision is undoubtedly the result of something done within the eye, 
the eflect of an active external agent, and the reaction of the mechan- 
ism; the chemical constituents of nervous matter, — ^perhaps the atoms 
of carbon or phosphorus are in some way changed or influenced by 
nerve impulses in infinitely rapid succession, the sensations of vision 
and color being the consequence. If it be objected that the foregoing 
statements are incredible, we reply that they are generally accepted 
by the most sober and cautious scientific thinkers. But they are really 
no more strange or impossible than many other of the miracles of being 
which science is constantly unfolding around us. We should observe 
a due modesty in criticising and assigning limits to the wonders and 
perfections of God's works. Dismissing the more purely theoretic or 
explanatory aspect of the subject, we now proceed to notice those 
properties and relations of colors which are the result of actual ex- 
amination. 



Fig. 34. 



v.— COMPOSITION AND MUTUAL INFLUENCE OF COLORS. 

157. White Light talicn to pieces. — If a ray of common white light 

be admitted, through a small aperture, into a dark room, and be made 

to strike upon a triangular piece 

of glas3 (prism), the white ray 

disappears ; it is turned from its 

course, and there falls upon the 

opposite wall an oblong colored 

image called the solar spectrum. 

It consists of seven bright colors, 

always found in a certain order, 

- .. , ... ,. vi • t -M * ' as shown in Fig, 34: but they 

Separation of white light into Newton s seven ^ o i j 

prismatic colors. pass into each Other gradually, so 

that it is difficult to tell where one ceases and another begins. New- 
ton assumed, as the result of this experiment, that white light is a 
compound principle, consisting of these seven colors, which he called 
primary, and taught that all other colors whatever are the result «f 
various commixtures of these. For convenience of representing the 
relations of colors, we may represent white light by a circle, and the 




NXTMBER OF PRIMARIES. 



89 



Fia. 85. 




colors which compose it by divisions of the enclosed space. lu that 
case the seven primaries of Newtox will be shown as in Fig. 35. 

158. IVewton's cxplauatioa of Colored Surfaces. 
— White light falls upon objects, and they ap- 
pear colored : how is this ? Newton replied : 
Dodies have not only the power of reflecting 
and transmitting light, but they can also de- 
compose and absorb it. A body appears 
white because it reflects back to the eye the 
white light that falls upon it, unaltered. When 
white light falls upon a surface and it appears 
MacTc^ it is absorhed and lost in the substance, 
and therefore does not return to make an impression upon the eye. 
But the blackest surfaces do not really absorb all the light, for then 
they would be invisible, and appear like dark cavities, presenting no 
surface. If the surface appears colored, it is because the white light 
is split up, or decomposed, one part being absorbed and lost, while 
the other is reflected to the eye, so that the object appears of the re- 
flected color. For example, grass absorbs all colors but green, which 
it reflects to the eye ; and in the same way the sky absorbs all but 
blue, and reflects that to the eye. Different surfaces reflect the pri- 
mary colors mixed in all manner of ways, and hence the endless 
modifications of color that meet the eye. 

' 159. But three Primary Colors. — A more simplified view of the com- 
position of colors has been propounded by Sir D. Brewstee, and 
generally received. He considers 
that instead of seven, there are 
but three elementary colors, red, 
yellow, and blue, and that the 
others are compounds of these. 
"We cannot produce red, yellow, 
or blue, by the mixture of any 
other colors ; but we can pro- 
duce all others by the various com- 
binations of these three. Beews- 
TER maintains, that even the colors 
of the spectrum are not absolutely 
pure, but that each of the three 
exists throughout its whole extent, although greatly in excess at the 
different points where they are visible. Blue, yellow and red being 
primaries, violet, indigo, green and orange are secondaries derived 



Fig. 86. 




90 



KELATION AND MUTUAL INFLUENCE OP COLORS. 



Fig. 37. 




Fig. 88. 



Fro. 89. 



from them. The separation of the impure or compound colors from 
the spectrum, leaving the three from which 
they are derived, is illustrated in Fig. 36. 
Orange is derived from the mixture of red 
and yellow ; green from yellow and blue ; 
and indigo and violet from blue and red. So 
that we have white light at last composed 
only of the three colors, as represented in 
Fig. 37. 

160. What are Complementary Colors. — The effect of a colox'cd surface 
is to decompose the white light which falls upon it, reflecting one 
portion, and absorbing or extinguishing the rest. We do not see any 

colored surface, except 
by the separation of the 
light which falls upon it - 
into two colored parts, 
the one visible, the other 
absorbed, Now it is evi- 
dent that the rays ab- 
sorbed, added to those 
which are reflected, make 
up the ordinary light. 
Hence whatever be the color reflected, that which is not reflected, 
and which is, therefore, wanting to complete the full set of colors which 

form white, and make 

out the full complement, 

is called the comple- 

EeS^ \ / \ \ ifnentary color. The part 

absorbed, or which does 
Yellow ') . i [ liU^ow ) Violet \ nnt appear, is the com- 
plementary of the color 
seen. This may be made 
perfectly clear by the 
circular diagram. If we 
lOok, for example, upon a red surface supposed to be presented in 
Fig. 38, yellow and blue are seen to be the colors necessary to com- 
plete it to white ; they are therefore the complement of red ; but 
yellow and blue form green, as shown in Fig. 39, which is therefore 
the true complement of red, that which it lacks to make white. If we 
k)ok upon a yellow surface (Fig. 40), blue and red are deficient ; blue 




Fig. 41. 





A NEW SYSTEM OF ARRANGING TITEAf. 91 

and red produce violet, therefore violet is the complementary of yel- 
low, as seen in Fig. 41. j^,^^ ^.^ ^^^^ ^^ 
A^ain, we look upon 
blue (Fig. 42) ; red and 
yellow are required to 
complete the circle into 
whiteness ; but red and 
yellow make orange, 
therefore orange is the 
complement of blue, as 
is shown in Fig. 43. 

161. Tints and Shades, Tones and Scales. — These terms have formerly 
been employed in the most loose and mdefinite way ; they have, how- 
ever, now acquired a kind of scientific precision. The tones of a color 
are those aspects which it presents when altered from its maximum 
of brightness or highest intensity, by mixing with it either white or 
black : if we take the purest and brightest red as a standard, say car- 
mine, and mingle various proportions of black with it, we of course 
darken it and get deeper tones of red. If we mingle white with it, 
we lighten it and get lighter tones of red. By the addition of black 
the red is said to be shaded^ by the addition of white it is tinted. 
Each color, in this case, is a tone of red, and the whole series of tones 
constitute a scale — the red scale. It may consist of ten, twenty, or 
fifty tones, according to the quantities of black and white successively 
added. In the same manner we make tones of orange and get an 
orange scale, tones of blue and get a blue scale, and so each color has 
its scale, in which it moves in two directions, from its normal or 
standard point, towards black and towards white. 

162. What arc Hues? — A hue is the result of the movement of a 
color, not in the direction of black or white, but of some other color 
out of its scale. If a little blue be mingled with red so as to change 
it slightly, the red still predominating, a hue of red is produced. So 
if blue be tinged in a similar manner by any color, hues of blue re- 
sult. In the same way are produced hues of orange, yellow, violet, 
green, &c. 

163. Chcvrenl's scheme for showing the relation of Colors. — A plan has 
been suggested by M. CnEVREHL, of France, for representing the com- 
position and relations of colors, in an extremely simple and effective 
way. It clears the mist from the subject, and not only discloses it in 
a beautiful order, but is very valuable for practical purposes. It is 
represented by the diagram (Fig. 44). The outer circle represents 



92 



KELATION AND MUTUAL INFLUENCE OF COLOKS. 



black, the centre white. The radial lines passing from the centre to 
the circumference represent scales of color, each dot indicating a tone. 
Each scale comprises ten tones. Take the red scale for example. The 
larger dot at Ti represents the place of its normal, or type of the purest 
red ; from that point toward the circumference it is shaded down to 
black, and in the other direction it is tinted up to white. The same 




I^ELLOVt 



/Orange 



RID 



Plan of Cheveetjl'8 Chbomatio CraoLEs, illustrating the principle of comi/Iwnentary 
colors, tints, shades, tones, hues, and scales. 

with yellow ; its normal is at a, and that of blue at c. From these three 
primaries all the rest are derived. Midway betweea yellow and blue is 
the scale of green, which results from their combination in equal pro- 
portions, half blue and half yellow. Midway between green and blue 
is a scale that we might call a greenish blue. It is only one-quarter 
of the distance from blue to yellow, and therefore is three-quarters 

/ 



now THEY MAY BE EXHIBITED. 93 

blue, and one-quarter yellow, — a hue of blue. Space or distance 
represents proportions of color. It will be seen that colors may be 
altered in two ways, that is, may move in two directions — along their 
scales, by admixture with white or black, producing tones^ and out of 
their scales, in the direction of the circles, producing hues. The dia- 
gram represents twelve scales, with ten tones on each scale, giving 
an arrangement of 120 colors, each having a definite, known compo- 
sition. With 24 scales, and 24 tones on each scale, we should have a 
scheme of 5Y6 colors. 

164. Making a Chart with the real Colors. — An instructive exercise is 
to produce such a chromatic chart with the actual colors. Make a 
circle upon paper a foot in diameter, designed for twelve scales of ten 
or twelve tones. From a box of paints select carmine for the normal 
red, gamboge for the normal yellow, and Prussian blue for the normal 
blue. By mixing the blue and red with a pencil brush in equal pro- 
portions, the violet is produced, and by varying the proportions all 
the hues between blue and red are obtained. By mixing blue and 
yellow, green, greenish-yellow and yellowish-green are made ; and by 
mingling red and yellow, orange, orange- yellow and yellow-orange 
are made. Thus all the hues are obtained. By mixing each with 
black and white, increasing the proportion of black regularly as you 
proceed outwards, and white as you go inwards, the scales will be 
formed. Familiar colors would at once locate themselves upon such 
a chart, so that we should understand their exact composition. For 
example, the crimson will be found near the red, but in the direction 
of blue, that is, it is red slightly blued, while scarlet is red, moved 
slightly in the opposite direction, toward yellow. So indigo is blue 
just started toward red. 

165. — How the Diagram shows Complementary Colors. — We determine 
the complementary of any color in a moment, by a glance at the sys- 
tem of circles. For example, we want the complementary color of 
red ; this is formed by the union of blue and yellow, producing green. 
Green, therefore, which is the complement of red, is placed exactly 
opposite to it on the diagram. So, opposite blue we see its comple- 
ment orange, and opposite yellow, violet, which is its complement, and 
also the contrary ; the complement of green is red ; of orange, blue ; 
of violet, yellow. So of all the scales, no matter how many are 
formed, their complements are seen on exactly opposite lines of the 
circle. The complement of red-orange is observed to be blue- 
green ; of a reddish-violet, it is greenish-yellow, and so on round the 
whole circle. We may even say that the complement of black ia 



94 RELATION AND MUTUAL INFLUENCE OF COLORS. 

white, and of white, black, — of a deep tone on one side, it will be a 
light tone on the other. Thus the complementary color of a deep 
tone of green will bo a correspondingly light tone of red ; of a light 
tone of violet, it will be a deep tone of yellow. By means of the dia- 
gram, therefore, the complementary of any of the one hundred and 
twenty colors can be found by any one in an instant ; a fact of much 
practical importance, as we shall soon have occasion to see. 

166, — What is meant by Complementary Contrast. — By a glance at the 
diagram it will be seen that the complementary of any color is its 
exact opposite. It is the color which differs from it the most possi- 
ble ; therefore it is in strongest contrast to it. Complementary colors 
are, hence, contrasted colors, and their relation is commonly indicated 
by the term complementary contrast. 

167. Luminous and sombre Colors. — It will be noticed that the three 
normals (Fig. 44) of red, yellow, and blue (represented by the larger 
dots), are not all located at equal distances from the circumference 
or centre. The reason of this is obvious. Yellow is a light, and blue 
a dark color. The natural position of yellow, therefore, at its height 
of intensity, is nearer to the white than to the black, and the natural 
position of bright blue is much nearer to the black than to the white, 
while red is intermediate. For this reason it requires more tones to 
shade yellow down to black than it does blue, and more also to tint 
blue up to white than it does yellow. Colors are thus divisible into 
luminous and sombre. Those into which yellow enters most largely, 
belong to the first class, and those consisting mainly of blue, to the 
second, red forming a medium color. 

168. Grays and Browns ; Pure and Broken Colors. — Grays result from 
the simple mixture of black and white. Browns are the result of 
mixing black with the various colors. The deeper tones of all the 
scales upon the diagram are browns. A color which has no black in 
it is said to be pure, while the addition of black produces a irolcen 
color. The browns are therefore all broken colors. A color may be 
broken, however, without directly adding black ; the three primaries 
mixed in certain proportions produce this effect. If a little blue, for 
example, be added to orange, it neutralizes a portion of the yeUow 
and red, breaking the color and starting it towards black, 

169. No Colors perfectly pure. — We must guard against the error of 
supposing that in practice we meet with any such thing as a pure or 
perfect color. Even those of the spectrum or rainbow are not per- 
fect ; Beewster has shown that the very brightest is contaminated by 
others. But when we leave the spectrum, and begin to deal with the 



EFFECTS OF COMPLEMENTAEIES. 95 

commoner aspects of colors, paints, dyes, &c., their imperfections be- 
come much more obvious. "We are to regard a red surface as reflect- 
ing to the eye, not a simple and perfect red, but along with the red a 
certain portion of the other colors of the spectrum, which have the 
effect of weakening and lowering the red. The true statement is, that 
the sensation of red is the result only of the •predominance of that 
color. It is the same with all the colors we see ; others are more or 
less mixed with them, which impair their brightness. 

170. How Colors mntaally improye each other, — The action of colors 
upon each other is not a matter of hap-hazard, and although it was 
long inexplicable, and half suspected to be a field where nature ca- 
priciously refused to be curbed by rules, yet science has at length dis- 
covered the reign of law in the domain of colors. Some combinations 
of colors are pleasing to the eye, and others disagreeable ; some are 
harmonious, and others discordant. The harmonies of color are of 
several kinds, but the fundamental and most important one is the 'har- 
mony of complementary contrast. If a purchaser be shown succes- 
sively a dozen pieces of bright-red cloth by a shopkeeper, those last 
seen will be declared much inferior in intensity of color to the first, 
such being the actual appearance which they present to the purchaser's 
eye. If now the buyer's attention be directed by the merchant to 
green stuffs, they will appear extremely bright, unnaturally so ; and 
if the eye recur again to the reds, they will look much finer than 
before. Eed and green viewed in this way have the mutual effect of 
improving each other. It is the same if the two colors be placed side 
by side and observed together ; they will so heighten each other's in- 
tensity as to appear much brighter and purer than when they are 
viewed separately, that is, when the eye cannot be directed from one 
to the other. If now we take yellow and violet, or blue and orange, 
or violet-red and yeUow-green, and observe them in the same manner, 
we shaU get the same result ; their brilliancy and clearness wiU be 
mutually heightened. But these colors are complementaries of each 
other ; complementaries then, when viewed together, improve each 
other. They are the most opposite or contrasted, and therefore the 
pleasing effect they produce upon the eye is denominated Harmony of 
Complementary Contrast. These effects are experimental facts which 
may be verified by any one. Take six circular pieces of paper, say 
an inch and a half in diameter, and color them respectively red, orange, 
yellow, blue, green, and violet. Place each one separately on a sheet 
of white paper, and then, with a thin wash of color, tint the white 
paper around each circle with its complementary color, gradually 



96 RELATION AND MUTUAL INFLUENCE OP COLORS. 

weaker and weaker as the tint recedes from the colored circle. If 
now the red circle be placed upon the sheet that is colored green, it 
will be made to appear greener ; so if the green circle be placed upon 
the reddened sheet, the latter color will be at once brightened. It will 
be found upon trial, that each color when viewed with its comple- 
mentary, increases its intensity or improves it. "We get by such exper- 
iments two kinds of result ; first, a successive change where one color 
is viewed after another ; and, second, a simultaneous change when 
both colors are seen at once and together. Both these effects require 
to be explained, and first of successive contrast. 

171. Colors exert an inflnenee npon the Eye. — Colors a^ppear to exist 
upon the surfaces of external objects, but we must not forget that 
their real seat is in the eye itself ; that is, external bodies so modify 
the light, that it produces within the eye different effects, which we 
name colors. Colors are sensations, or nerve-impressions, the result 
of something accomplished within the optic organism. Thus we say 
snow is white, and blood is red ; meaning thereby that snow so influ- 
ences the light, that it originates within the organ of vision a sensa- 
tional effect which we style white ; while blood so modifies the light 
falling upon the nerve of the eye as to cause the perception of red. 
A.S color thus finally resolves itself into different modes of affecting 
the eye^ we might naturally expect that both the agent and its organ 
would react upon each other, — colors producing changes in the eye, 
and the eye producing changes in colors, more or less considerable, 
according to circumstances. The eye being a part of the bodily sys- 
tem, and governed by general physiological laws, is subject to the 
same vicissitudes of varying activity, acute and blunted susceptibility, 
as other parts. "We shaU now notice the change that takes place, only 
60 far as colors are themselves atfected ; deferring to another place an 
examination of the influence of colored light upon the eye in refer- 
ence to its health (253). 

172. Duration of Impressions npon the Retina. — Impressions continue 
upon the nerve of the eye about one-sixth of a second after the object 
is removed. For this reason, a torch whirled swiftly round appears 
as a continuous streak or ribbon of fire. But the eye continues to be 
affected for a much longer time ; although it is not, as we might at 
first suppose, by a feeble, lingering impression left npon it, which 
gradually fades out after the object is withdrawn from sight. If there 
were a continuance of the perception of an object after its removal, 
the effect of viewing another object would be the mixture of two 
colors. For example, if a bright blue object were seen, and then the 



THEV AFFECT EACH OXUEU XliliOUaU THE EYE. 01 

eye suddenly directed to a red, the effect would be a perception of a 
mixture of the two, or violet, aud this would remain until the first 
impression, or blue, faded away from the retina, after which the red 
object alone would be perceived. But such is not the case. 

173. The Eye loses its sensibility to Colors, and demands their Comple- 
mcutaries. — The influence of any color upon the eye is to diminish or 
deaden its sensibility to that color ; it gets fatigued in looking at one 
color for some time, so that it appears less bright. If, for example, 
the gaze be directed for a time upon a bright red object, that part of 
the retina upon which the image is impressed, becomes exhausted by 
the action of the red color, and partially blinded to its brightness ; 
just as the ear may be deafened for a moment by an overpowering 
Bound. But the effect does not stop here. If the eye be averted from 
the red and directed to white, the red contained in the white will not 
produce its natural effect, while the balance of the colors in white, 
blue, and yellow, make their proper impression upon the eye, pro- 
ducing green. Thus the eye, dulled to one color, has a tendency to 
see its complementary. If we place a red wafer upon a sheet of white 
paper, and fix the gaze upon it steadfastly for some time, and then toss 
it off, we shall see a spectral image of the wafer upon the paper, iut it 
will ie green. The wafer so extinguished the sensibility to red upon 
a certain portion of the retina, that when it was removed, the eye 
saw the white, mimis the red., that is, green. In like manner, if the 
eye be impressed with green, it loses its sensibility for it, so as again 
to decompose white and see red. If blue is observed, the impressi- 
bility of the nerve of sight is lowered for that color, so that white 
light is seen without its blue, and orange appears, which is the com- 
plementary of blue. In like manner the observance of yellow creates 
a tendency to see violet, and in the same way the effect of any color 
whatever, is to dispose the eye to see its complement. If we gaze at 
the sun at sunrise, when of a ruddy appearance in consequence of his 
rays being strained of their blue and yellow as they pass through the 
damp atmosphere near the ground, an image will be generated by the 
eye formed of these missing rays, and, therefore, green. When he 
has ascended higher and become of an orange yellow color, the image 
will be dark violet. It is well known that in looking at the sun 
through colored glasses at the time of an eclipse, spectres of the solar 
disk are sometimes produced which continue for a time before the eye. 
The color of these is always complementary to the color of the glass 
through which the sun was viewed. 

174. Simnltaneons contrast of Colors. — But colors placed side by side, 

5 



98 RELATION AND MUTUAL INFLUENCE OF COLORS. 

exert upon each other, simultaneousli/^ an influence that can hardly be 
accounted for by the theory which explains successive contrast. Tho 
effect is of the same kind, — contrasted colors are augmented in bright- 
ness, but it results from the equal action of both colors upon the eye 
at the same time. It has been stated that surfaces reflect to the 
eye rays of other colors beside those which appear. No surface can 
so perfectly analyze the white light which falls upon it, as to absorb 
all of one color, and reflect all of another. It appears of the color 
of the predominating ray, though more or less of the remaining colors 
of Avhite light are reflected also, and diminish its purity. "We look 
upon a red ; it is not perfect, because other colors not red, but the 
opposite of red, are mingled with it and i-educe its effect. We gaze 
separately upon green ; it is vitiated by rays coming from it that are 
not green, but its opposite. Now if we could clear away or destroy 
these vitiating rays, we should improve both colors, and this is ac- 
tually done by placing them side by side. The reducing colors, which 
are active when the surfaces are viewed separately/, seem to be, in 
some way, neutralized when they are brought together, and the com- 
plementary of each is thrown upon the other. 

175. How associated Colors injure each other. — If certain combina- 
tions of color alter each other for the better, it is easy to see how 
other combinations must act in other ways for the worse. If the 
mutual effect of colors most contrasted be to intensify and exalt each 
other, it follows that if those most nearly alike are associated to- 
gether, they will vitiate and injure each other. What the exact effect 
will be, may be seen at once by inspecting the chromatic diagram. 
The complement of violet is yellow. If violet bo associated with 
yellow, therefore, the only effect it can produce is to make it yellower ; 
but suppose it be placed beside other colors, the result must be a ten- 
dency to yellow them all. Violet placed beside green drives it out of 
its scale (see diagram) toward yellow. It was half yellow before, bu* 
the effect of violet is to increase the proportion of this element, and 
thus produce a new hue of yellowish-green. If violet be placed 
beside orange, which is also half yellow, it is moved out of its scale 
in the same direction as before toward yellow, a hue of yellowish 
orange being produced. As orange and green are already half yellow, 
it is obvious that the effect of adding to them a little more yellow will 
not be so marked as when this color is cast upon those which do not 
contain it. Violet, beside blue, stains it of a greenish hue ; while 
beside red it changes it to scarlet. By tracing these effects out upon 
the diagram we at once get at the general law of the mutual influence 



HOW THEY AEE CHANGED BY CONTRAST. 



99 



of colors. A color placed beside another tends to make tTiat color as 
different as possiMe from itself. In the case of violet just alluded to, 
by reference to the diagram it will be seen that the color naturally 
farthest from it, by its very constitution indeed exactly opposite to it, 
is yellow. Now if bright violet be placed beside the yellow scale, it 
will drive every tone of that scale one or two steps back, away from 
itself, by making them all still yellower, and you will notice that the 
effect of violet upon the other colors, by throwing yellow upon them, 
is to start every one of them away from itself in the direction of its 
antagonist, which is the yellow. If traced out it will be seen that the 
effect of any other color is precisely the same. The complementary 
of any color thrown upon another renders it more unlike, or increases 
the difference between them. 

176. Contrast of Tone. — The effect of viewing white and black to- 
gether is to heighten the contrast between them, and so with the in- 
termediate tones of a scale of white and black. The accompanying 
wood-cut (Fig. 45) affords an im- 
perfect illustration of this effect. 
It consists of five bands, shaded 
successively deeper and deeper 
from left to right. As the eye 
glances at the scale, the bands 
appear darker at their left bor- 
ders and lighter at their right. 
But this appearance is an effect 
of contrast ; for if we take two 
slips of paper with straight edges, 
and cover all the diagram but 
any single band, its surface will be seen to be perfectly uniform. When 
viewed together, however, there is a heightening of the real differences, 
the light tones seem lighter and the dark tones darker, almost as if 
the intention was to represent fluting. It is so with the different 
tones of any color which has been shaded with black or tinted with 
white. If we place two different tones of the same color together, 
they always alter each other's intensity ; dark tones making adjacent 
light ones appear still lighter, and light ones making dark tones seem 
still darker. This is, perhaps, because the absence of light in the 
dark color renders the eye more sensitive to the white light of the 
lighter color, and on the contrary the dark color appears darker, be- 
cause the white light of the lighter color destroys the effect of tlie 
small amount of white light reflected by the other. Thus if we place 




lUustratins the effect of contrast of tone. 



100 llELATION AJSTD MUTUAL INFLUENCE OF C0L0E3. 

a dark red beside a light rose-color, or a deep yellow iu contact with 
a straw-color, they will, as it were, push each other further apart, the 
light tones in both cases appearing lighter, and the deep ones deeper, 
so as to deceive the eye in regard to the real depths of their colors. 
Thus for tones as well as hues the law of Cheveetil holds good. " In 
the case loliere the eye sees at the same time two contiguous colors^ they 
will appear as dissimilar as possible, loth in their optical composition 
and the height of their tone^ 

177. Harmonies of Analogy. — The employment of glaring or intense 
colors in many cases, as often in dress, is not admissible by the rules 
of cultivated taste. It is chiefly among the rude and uncultured 
that Ave remark a passion for gaudy and flaunting colors. With the 
progress of a refined civilization there is a tendency to the employ- 
ment of more subdued colors in personal and household decoration. 
Not by any means that good taste requires the total rejection of bright 
colors, but only that they be used with skill and discretion — be ameli- 
orated by combination, so as not to produce staring and stunning effects, 
or strong and deep contrasts which often offend tlae eye. Harmonies of 
complementary contrast are to be first and chiefly sought in chromatic 
arrangements ; but these are comparatively limited, and in the demand 
for variety, other concords are found, which, although less striking, 
often give beautiful results. In studying the best arrangement of 
colors to produce a harmonious grouping, regard must be had to the 
kind of eflfect required, whether lively, medium or sombre. In one 
case, bold striking contrasts will be sought, in another mild ones ; and 
again, rejecting contrasts altogther, we may get an agreeable efiect by 
grouping together similar or analogous colors. Harmonies of analogy 
may be produced in three ways. First, we may arrange the different 
tones of a single scale in a series, beginning witli white and terminating 
with brown black, leaving as nearly as possible equal intervals be- 
tween them. This will produce a pleasing result. The greater the 
number of tones the finer will be the efiect. Second, we may asso- 
ciate together the hues of adjacent scales, all of the same tone, and 
often produce an agreeable analogy. But sometimes colors of near 
scales mutually injure each other, as blue and violet ; the complemen- 
tary of blue, which is orange, being thrown upon violet gives it a 
faded and blackened appearance ; while the complementary of violet, 
which is yellow, falling upon blue turns it to green. Sometimes when 
one color is injured we may sacrifice it to give prominence or relief to 
another. Third, a pleasing harmony of analogy is produced by view- 
ing groupings of various colors through a colored medium that casta 



EFFECTS OF DIFFERENT GROUPINGS. 101 

its own peculiar hue over the whole, as when we view a carpet it 
light that comes through a stained glass window. 

178. Circnmstances which disturb the influence of Colors. — Various con 
ditions exert a modifying effect upon the mutual action of colors. 
The result may be greatly influenced by the shape of the object, and 
the manner of its exposure to light. The surface of a red curtain, 
for example, hung in folds, appears of different hues, the parts most 
exposed to the light being changed in the direction of scarlet, while 
those more protected fi'om it are shaded so as to approach a crimson. 
The condition of surfaces is also important. When tbey are glossy 
then* colors affect eacb other much less, and a bad association may be 
concealed or overlooked where the elegance of symmetry of the 
object, or the light and shade are so related, or our ideas are in some 
way so associated with it as to draw the attention from the ill effects 
of the colors. It is often thus that flowers present bad associations, 
yet our feeling concerning them is such that we are not offended as 
when we see the same upon flat unglossed surfaces. The flower of the 
sweet pea, for instance, gives us the alliance of red and violet, which 
mutually injure each other, though the green leaves set off the red 
and help the result. 

179. Effect of associating Colors with White. — All colors appear 
brighter and deeper when associated with Avhite, because its superior 
brilliancy renders the eye insensible to the white light which accom- 
panies and weakens the color. At the same time the white is tar- 
nished by the complementary of the color falling upon it. "White is 
60 intense that in all its arrangements with color, except perhaps light 
tones of yellow, there will be contrast. It may often be interposed 
with advantage between colors which injure each other. All the pris- 
matic colors gain by grouping them with white, but not in an equal 
degree, for the height of tone of the color makes a decided difference 
in the result. The deep tones of blue, red, green, and violet, contrast 
too strongly with white, while the light tones of the same colors form 
with it the pleasantest contrasts we can obtain. Oi'ange, the most 
brilliant of the colors, is almost too intense Avith white, while the 
deeper tones of yellow appear well with it. 

180. Effect of associating Colors with Black and Gray. — Black is agree- 
able if associated with almost any color. With their light tones it 
contrasts well, making them appear lighter, and being itself darkened, 
while their som1)re complementaries thrown upon the black scarcely 
affect it as its surface reflects so feebly. Witli the deep tones of the 
Bcales it forms harmonies of analogy, although their luminous com- 



102 PRACTICAL SUGGESTIONS IN COMBINING COLORS. 

plementaries, especially those of blue and violet when falling upon 
black, deprive it of its vigor, and tend to. make it look faded. Gray 
being' intermediate between black and white, it is used where white 
gives too strong a contrast, and black makes the combination too 
sombre, as with orange and violet, green and blue, green and violet. 

VI.— PRACTICAL SUGGESTIONS IN COMBINING COLORS. 

181. Articles of Dress. — A recollection of the foregoing principles 
may enable us to avoid gross errors in combining colors. Thus a lady 
would hardly trim a violet bonnet with blue flowers, or an orange 
with yellow ribbon, while she would do well to trim a yellow bonnet 
with violet or blue, and a green one with rose-red or white, and to 
follow the same general rule in arranging the colors of a dress. "We 
are not to overlook the effect of contrast of tone as well as color. A 
black coat that is much worn, will appear well in summer in contrast 
with white pantaloons ; but if put on over new black pants, it will 
appear older, rustier, and more threadbare than it really is. Stains 
upon garments are less apparent where there is considerable difference 
among the colors of the various articles of apparel, than where they 
are more uniform, the contrast among the colors rendering that be- 
tween the stain and the surrounding cloth less conspicuous. Colored 
articles of dress produce a deceptive effect in reference to the size of 
the wearer. The influence of dark or black colors is to make the per- 
son wearing them seem smaller, while white or light dresses causes the 
figure to appear larger than the real size. Large figures or patterns 
upon dresses and horizontal stripes make the person look short, while 
narrow vertical stripes on a dress cause the wearer to seem taller. 

182. Influence of Colors npon the Complexion. — Any colored objects, 
as bonnet trimmings or draperies, in the vicinity of the countenance, 
change its color ; but clearly to trace that change we must know what 
the cast of complexion is. This varies infinitely, but we recognize 
two general sorts, light and dark, or ilonde and 'brunette. In the 
blondes or fair-complexioued the color of the hair is a mixture of red, 
yellow, and brown, resulting in a pale orange brown. The skin is 
lighter, containing little orange, but with variable tinges of light red. 
The blue eye of the blonde is complementary to the orange of the 
hau". In brunettes the hair is black, and the skin dark, or of an 
orange tint. The red of the brunette is deeper or less rosy than that 
of the blonde. Now the same colors aflect these two styles of com- 
plexion very differently. A green setting in bonnet or dress throws 



HOW THEY AFFUOT THE COMPLEXION. 103 

its complemeut of red npon the face. If the complexion be pale and 
deficient in ruddy freshness, or admits of having its rose-tint a little 
heightened, the green will improve it, though it should be delicate in 
order to preserve harmony of tone. But green changes the orange 
hue of the brunette into a disagreeable brick-red. If any green at all 
be used, in such case it should be dark. For the orange complexion 
of brunette the best color is yellow. Its complementary, violet, neu- 
tralizes the yellow of the orange and leaves the red, thus increasing 
the freshness of the complexion. If the skin be more yellow than 
orange, the complementary violet falling upon it changes it to a dull 
palUd white. Blue imparts its complementary orange, which im- 
proves the yeUow hair of the blondes, and enriches white complexions 
and light flesh tints. Blue is therefore the standard color for a 
blonde, as yellow is for a brunette. But blue injures the brunette by 
deepening the orange, which was before too deep. Violet yellows the 
skin, and is inadmissible except where its tone is so deep as to whiten 
the complexion by contrast. Eose-red, by throwing green upon the 
complexion, impairs its freshness. Ked is objectionable, unless it be 
sufficiently dark to whiten the face by contrast of tone. Orange 
makes light complexions blue, yellow ones green, and whitens the 
brunette. Wliite, if without lustre, has a pleasant efiect with light 
complexions ; but dark or bad complexions are made worse by its 
strong contrast. Fluted laces are not liable to this objection, for they 
reflect the light in such a Avay as to produce the same cftecfc as gray. 
Black adjacent to the countenance makes it lighter. 

183. Arrangement of Flowers in a Bonqnet. — In grouping flowers, com- 
plementary colors as far as possible should be placed side by side, blue 
with orange, yellow with violet-red, and rose with the green leaves. 
On the contrary we snould avoid combining pink Avith scarlet or 
crimson ; orange with orange-yellow ; yellow with greenish-yellow ; 
blue with violet or violet-blue ; red with orange, or pink with violet. 
If these are to be inserted in the same nosegay, white should be inter- 
posed between them, as it prevents colors from acting injuriously upon 
each other while it heightens their tone. 

184. Best colors for Paper Hangings. — Dark paper for the walls is bad, 
because it absorbs too much light, and the room is not sufficiently 
luminous : this is especially true of rooms with a northern aspect 
where the sun never enters, for such apartments paper of the lightest 
tints should be used. We have seen that the complementaries of red 
and violet are bad for the complexion (181), red and violet are there- 
fore objectionable aa wall colors. Orange and orange yellow are 



104 PKACTICAL SUGGESTIONS IN COMBINING COLORS. 

fatiguing to the eye. Among the simple colors light blue, light green 
(314), and yellow, seem fittest for hangings. Yellow is lively, and ac- 
cords well with dark furniture and brunette complexions, but it hardly 
appears well with gilding. Light green is favorable to pale skins, 
deficient in rose, and suits with mahogany furniture. Light blue goes 
well with mahogany, is excellent with gilding, and improves blonde 
complexions. 'White and light gray, with velvet patterns the same 
color as the ground, are well adapted to a wall to be decorated with 
pictures. In selecting a lorder we should seek for contrast, so that 
it may appear, as it were, detached from the hangings with which it 
is associated. If there is a double border, an interior one of flowers 
and an exterior one, the last must be deep in color and much smaller. 
Yellow hangings should be bordered with violet and blue mixed with 
white. Green will take any hue of red as a border. White hangings 
should have orange and yellow. Gray uniform hangings admit of 
bordei's of all colors, but no strong contrasts of tone ; gilt borders do 
well with them. If the gray be colored, the border should be com- 
plementary. The neutral tints of paper, drabs, stones, &c., are par- 
ticularly appropriate for picture-galleries, — they produce good effects 
in other rooms with well chosen borders and mouldings. 

185. Pictures, Frames, and Gilding. — As the picture itself is the valu- 
able object upon which we wish to fix attention, it is not in good taste 
to divert or distract it by gaudy and conspicuous surroundings and 
ornaments ; hence simple framings, just enough to isolate or separate 
the picture, are preferable. Gilt frames will do with large oil-pictures, 
particularly if there is no gilding represented in the picture. Gilt 
frames also answer well for black engravings and lithographs, but a 
little margin of white should be left around the subject. Black 
frames, by their strong contrast of tone, tend to lighten the aspect of 
the picture, and often spoil a good engraving by taking the vigor from 
its dark colors. Gray frames are good, especially if the picture have 
a leading color, and the gray be slightly tinged with its complementary. 
As a rule, neither the frame nor the border within it should ever be 
sufl^lered by their brightness, color, or ornaments, to injure the colors, 
shadows, or lights of the picture. The best ground for gilt ornaments 
is blue, because its complementary intensifies the color of the orna- 
ments ; hence shrewd shopkeepers who sell gilt articles line their show- 
cases with blue, A bright green ground reddens and improves gilt 
objects. Eed and orange pervert the gilt tint, and black lightens and 
weakens it (144). 

186. Assortment of Colors for Fnrnitnrc. — In determining the colors 



COMBINATIONS IN HOUSE-FUENISHING. 105 

to be used in furnishing a room, the amount of light is an important 
consideration ; dark colors, as dark blue, crimson, &c., require nmch 
light to be seen distinctly. Eed curtains redden the transmitted light 
of day, and impart this color to the countenances it falls upon. But 
by artificial or reflected light, red curtains and furniture dispose the 
eye to see green in the countenances of people in the room, while 
green curtains make the countenances rosy. Chairs and sofas, when 
complementary to the paper upon the wall, are most favorable to dis- 
tinct vision ; but for collective effect, when we desire to present the room 
as a unit, bold and complementary contrasts are inadmissible, as they 
fix the attention too much upon distinct and separate objects. It is 
better, therefore, in arranging for chairs and hangings to seek contrast 
of scales, or hues and harmonies of analogy. In trimming chairs and 
sofas, vivid reds should never be used with mahogany, for they are so 
bright that the mahogany loses its beauty, and looks no better than 
oak or black walnut. Crimson velvet is often used with mahogany 
because of its durability ; but the colors are so nearly allied, that a 
strip of green or black galloon should be used as a border to the stutf, 
or a narrow cord of golden yellow with gilt nails. Green or green 
grays are best suited to trim mahogany and red-colored woods. In 
using diiferently colored woods we can assort the colors of their trim- 
mings according to the rule previously laid down. The carpet should 
be selected with reference to the other furniture of the room. If 
mahogany is used, the carpet should not have a predominance of red, 
scarlet, or orange in it. If the furniture exhibit various and vivid 
colors, the pattern of the carpet should be simple and sober, as gi*een 
and black for example, whUe if the furniture is plain the carpet may 
be gay. 

VII.— PRODUCTION OF ARTIFICIAL LIGHT. 
1. The CnEMisTKY of Illumination. 

187. Natural and Artificial Lig;ht. — As respects its sources, light is of 
two kinds, natural light, or that which comes from the sun, moon 
and stars ; and artificial light, or that which man obtains at will by 
various means. Artificial light may be procured by electricity, gal- 
vanism, and phosphorescence ; but the ordinary method is by that 
kind of chemical action which is termed combustion^ the nature of 
which has been explained when speaking of heat. 

188. Light emitted by ignited Bodies. — AU solid substances shine 
when sufficiently heated. The temperature at wliich they become 

5* 



106 PKODUCTION OF ARTIFICIAL LIGHT. 

luminous, according to Dr. Dbapee, who baa lately investigated the 
subject, is 977° F. He enclosed a number of different substances 
with a mass of platinum in a gun barrel ; upon beating and looking 
down the tube, he saw that they all commenced to shine at the same 
moment, and this, even though, as in the case of lead, the melted con- 
dition bad been assumed. The color of light emitted from ignited 
substances was found to depend upon the degree to which they were 
heated. Dr. Deaper showed that as the temperature rises, the 
colored rays appear in the order of their refrangibility, first red, then 
orange, yellow, green, blue, indigo and violet, are emitted in succes- 
sion. At 2130° all these colors are produced, and from their commix- 
tui'e the substance appears wliite-hot. The same Investigator also 
found, that as the temperature of an ignited solid rises, the intensity 
of the light increases very rapidly ; platinum at 2600° emitting almost 
forty times as much light as at 1900°. 

189. All onr illamination comes from Imrnlng Gas — The foregoing Ex- 
periments were made upon solid substances, but their results do not 
hold true for gases. These require to be heated to a much higher 
temperature before beginning to shine ; and when they do become 
luminous they emif but a feeble light. If we hold a piece of fine iron 
wire in the hot air which streams uj) above a lamp flame it wiU 
quickly become red, showing that a degree of heat which makes the 
metal shine does not make the air luminous. And yet all ordinary 
illumination comes from the combustion of gases. We use those ma- 
terials for lighting, which in burning produce flame ; and flame is 
burning gas. All substances which can be used for light must be 
capable of conversion into the gaseous state. The process is essentially 
the same, whether we burn the illuminating gas which is brought to 
our dwellings in underground pipes, or the liquid oil, or solid sjjerma- 
ceti. In the first instance the gas is manufactured on a large scale 
from solid bituminous coal or resin ; in the latter cases the liquid oil 
and solid tallow or wax are converted into gas at the time of iurning. 
In all cases the light proceeds from a rising stream of gaseous mattei 
which is lighter than the air, and therefore tends to ascend. 

190. What takes place in the Laminoas Flame. — The materials used 
for illumination contain hydrogen and carbon, and the gas they yield 
consists of these elements more or less pure. Hydrogen, as we have 
before stated, is the lightest and most ethereal of all substances (76). 
The gas which gives rise to flame in illumination is therefore com- 
pound — a hydro-carbon. In burning, the oxygen of the air combines 
with these two elements, but it is not attracted to them equally. It 



CHEMISTRY OF ILLUMINATION. 



10^ 



Fig. 46. 




Fig. 4T. 



seizes upon the hydrogen first, burning it witli an intense heat, and 
the production of water. As the hydrogen combines with oxygen, it 
abandons the carbon, which is thus set free 
in a pure state. Now pure carbon is always 
a sohd. As the hydrogen leaves it, therefore, 
it is set free in the form of- exceedingly mi- 
nute solid particles in the midst of the heated 
epace, — those heated to redness, yellowness, 
or whiteness, become luminous, and are the 
real sources of the light. The carbon par- 
ticles remain suspended in the flame but for an in; taut ; they are 
themselves quickly burned and converted into carbonic acid.* 

191. How these facts may be shown. — If we hold a piece of clean 
cold glass a short distance above a candle flame (Fig. 46), a fine dew 
will be seen deposited upon it, which is the water generated within 
the flame. If a piece of white 
earthen be lowered over the 
flame the combustion is in- 
terrupted, and the uncon- 
sumed particles of carbon are 
deposited upon the white 
surface, thus proving that 
they exist free in the flame. 
If an inverted tumbler be 
held above a flame, so that 
the rising current may enter 
it (Fig. 47), and then it be 
closed with a card, set down, and a little clear lime-water poured into 
it and shaken, it will become milky from the combination of the car- 
bonic acid with the lime, which shows that the former substance was 
generated within the flame. 

192. Admirable simplicity of the Lairs of lilnmination.— There is a 
wonderful simplicity and beauty in this chemistry of illumination. 
The same active principle of the air which animates the living body 
and nourishes the fires which warm us, is also the awakener of light. 
All artificial illumination that we employ is due to the chemical energy 
of oxygen gas. The hydro-carbon compounds, upon which oxygen 
acts, are not only universal as life itself, being produced in all kinds 




• See the author's Atlas of Chemistry and Chemical Chart of Colored Diagrams, 
Ulustrating combustion and illumination 



108 PRODUCTION OF aKTIFICIAL LIGHT. 

of plants and animals, but the very crust of the globe is stored with 
endless accumulations of them. The hydrogen combines with and 
condenses a much larger amount of oxygen than any other element, 
and consequently produces a great heat. But the burning of these 
pure gases, although the heat is so high, hardly creates a perceptible 
light. To get illumination, solid matter is' required. Accordingly the 
lightest and most subtle of all gases, hydrogen, is associated with car- 
bon, the most refractory of all solids, which remains fixed without 
melting or vaporizing at the intensest heat which art can produce. 
These carbon atoms are set free, and shining brilliantly for an instant 
pass to the verge of the flame, and there unite with atmospheric 
oxygen, forming carbonic acid gas. The two products of combustion — 
vapor of water and carbonic acid — are both entirely transparent and 
invisible, so that although constantly formed within and around the 
flame, they do not eclipse or obscure it, but let the light pass freely 
in all directions. If oxygen were equally attracted to hydrogen and 
carbon, so as to burn them both at once, no solid particles would ha 
liberated in the flame, and consequently there could be no light. It 
is the successive combustion which takes place, — first the hydrogen 
burning and then the carbon, which gives rise to the luminous effect. 

193. Threefold form of Illnminating Substancest — The modes of burn- 
ing illuminating materials are various, depending upon their forms and 
properties. If capable of being used in a solid condition, they are 
moulded into a cylindrical or rod-like shape, and are called candles. 
If liquid, they are consumed from suitable vessels known as lamps; 
and if gases, they are simply jetted from minute orifices, by pressure 
upon the gaseous fountains. There are several things with respect to 
each of those methods of illumination which it is important to under- 
stand. 

2. iLLTJMISTATIOlSr BY MEANS OF SoLIDS. 

194. Adaptation of Tallow for Candles. — Those fatty and waxy bodies, 
Avhieh are sufficiently hard and solid to be handled, are worked into 
candles. They are made from tallow, stearine, spermaceti, and wax. 
There has been no way devised for burning those softer, fatty and 
greasy bodies Avhich lie between the Hquid oils and these firmer sub- 
stances. Tallow derived from beeves or sheep is most universally 
employed for candles. If they are mixed there should not be too 
great a proportion of mutton tallow or suet, as this contains a peculiar 
principle called hircin, which causes it sometimes to give a disagree- 
able smell, especially in hot Aveather. When of the best quality tallow 



ILLUMINATION BY MEANS OF SOLIDS. 109 

is white, firm and brittle. Alum is often put with it to harden it. 
The had quality of tallow candles is chiefly owing to their adulteration 
with hog's fat and cheap soft grease, which makes them smell, gutter 
and smoke. Good tallow candles will resist decomposition for two 
years, and are better after being preserved six or eight months. They 
should be kept from the atmosphere, and may he well preserved by 
being covered with bran. The place for their preservation should be 
cool and dry, as dampness mildews and damages them. Light turns 
them yellow. 

195. Cindles made from Stearic Acid. — The fats and oils are believed 
to consist of acids combined with a base ; at all events they are capa- 
ble of being decomposed and separated into those substances. The 
common base which exists in all fats and oils is, when set free, a sweet 
liquid called glycerin. The substances combined with it are stearic 
acid, margaric acid, and oleic acid. Stearic acid, combined with 
glycerin, forms stearin. Margaric acid, with glycerin, yields mar- 
garin ; and oleic acid, with glycerin, produces olein. Oleic acid, or 
olein, is the more liquid portion of oleaginous bodies ; it predominates 
in the fluid oils. Stearic acid, on the contrary, abounds in the hard 
fats and tallows ; it is their chief solidifying element. Margaric acid 
is less solid, being intermediate between stearic and oleic acids. The 
intermixture of these, in various proportions, gives rise to all the 
various grades of softness and solidity which the endless oil and fat 
tribe exhibit. Tallow contains seventy to seventy-five per cent, of 
stearic acid, and olive oil but twenty-five. Candles were at first made 
from stearin, and wer5 much superior to tallow ; but they are now 
manufactured from stearic acid, Avhich is more infusible. This sub- 
stance does not feel greasy to the touch, and is firm, dry, and brittle. 
It makes hard ant"! brilliant candles, which are considered nearly equal ^ 
to wax. 

196. Spermaceti aud Wax. — Spermaceti is a kind of stearine existing 
in the oil taken from cavities in the skulls of certain species of whales. 
It is manufactured into candles, which are of a beautiful silvery white 
aspect, translucent like alabaster, and having a high lustre. The wax 
of which bees construct their honeycomb is also used for candles. It 
is purified and bleached to a pure white. It burns with a clear and 
beautiful light, and is the most expensive matei-ial employed for illu- 
mination. Owing to its high price it is often adulterated. White 
lead, oxide of zinc, cljalk, plaster, and other earthy bodies may be 
detected by boiling the wax in water, when these substances will 
separate and fall to the bottom. If starch or flour has been used, they 



110 



PKODUCTION OF ARTIFICIAL LIGHT. 



may be detected by boiling and adding a solution of iodine, whicb 
will yield a beautiful blue color, tbe test for starcb. Yellow bees'-wax 
is often adulterated with resin, pea and bean meal, and many otbei 
substances. Tbe former may be detected by tbe smell, and tbe latter 
by tbe iodine solution. 

197. Stractnre of Candles— OCSce of the Wick. — The common burning 
,andle affords a beautiful illustration of tbe general principles of illu- 
mination. If we should attempt to burn solid tallow or wax in the 
lamp to produce light, it would be found very difficult to set it on fire, 
as it would melt away long before it could ignite. But if at length 
made to burn, a much larger amount of tbe combustible would be on 
fire than the air would perfectly consume ; there would therefore be 
a thick smoky flame instead of a clear white light. Some contrivance 

is hence needed to avoid this result and regulate the com- 
bustion, and this is secured by jjlacing cotton fibres within, 
the combustible, which form the wicK These fibres are 
placed parallel in the axis or centre of the caudle. When 
the wick which protrudes at one end is set fire to, it ra- 
diates heat downwards, so as to melt the material of the 
candle, and form a hollow cup filled with the liquid com- 
bustible around the wick-fibres (Fig. 48). The flame is 
fed from this cup or cistern by the wick, which dra>ws or 
sucks up the oily liquid exactly as a sponge or towel 
draws up water, by what is called the force of capillary 
attraction, or the attraction of small tubes for liquids. 
fronnhe'ci'stirn In this case the spaces between the fibres act as tubes, 
of oil below, and^ttract upward the liquid fat or wax. 

198. The burning Candle a miniature Gas-Factory. — We thus see that 
the candle is a kind of lamp which constantly melts its own combus- 
tible. From the reservoir the wick draws up the liquid material to 
the centre of the flame. Here, in the midst of a high heat, and cut 

off from the air, it undergoes another change 
exactly as if it were enclosed and heated in 
the gasmaker's retort, — it is converted into 
gas. The candle-flame is not a solid cone of 
fire. If we lower a piece of wire-gauze or 
broken window-glass over the flame (Fig. 49), 
we shall see that the interior is dark, and that 
what we regard as the flame is really but a 
thin, hollow, luminous shell of fire smTOunding 
This space is filled with the hydro-carbon gas 





The candle-flame hollow. 



the dark inner space. 




ILLUMINATION BY MEANS OF SOLIDS. Ill 

mannfiictured from the liquid tallow, stearine, spermaceti, or wax, 
drawn up by the wick. This may be directly shown. If one end of a 
glass tube, having a bore y of an inch, be introduced into a candle-flame, 
as seen in Fig. 50, the gas will be conveyed away „ ^ 

through it, and may be lit at the other end, thus 
exhibiting a miniature gas manufactory, pipe and 
jet, "When a candle is blown out, gaseous pro- 
ducts of distilled and burnt tallow continue to 
rise, emitting a disgusting odor, and the candle 
may be re-lit by applying a light to the smoky 
stream of combustible gas which will convey 
the flame back to the wick. It is the hydro- 
carbon gas that is really burnt and produces the 
light, the hydrogen and carbon being successively 
consumed, as we have seen, at the surface, or The interior of the candie- 

■L . 1 • • J. i. • i.1 iT_ ilame filled with gas. 

where the au* comes in contact with the gas. 

199. Interference of the Wick with Light. — As the candle consumes 
downward, the wick of course rises into the flame. In a short time 
it becomes so much lengthened as to interrupt the combustion and 
interfere with the light. Particles of iinconsumed carbon are gradu- 
ally deposited upon the wick, forming a large spongy snufl:" which 
nearly extinguishes the light. Peclet found that if the intensity of 
the light from a freshly snuflied candle be represented at 100, if left 
without being snuffed, its brightness is reduced in 4 minutes to 92, in 
10 minutes to 41, in 20 minutes to 32, and in 40 minutes to 14, al- 
though the consumption of the candle remained the same. Eumfoed 
fovad that the brilliancy of an unsnufled candle was reduced f in 29 
minutes. To prevent this annoyance and the necessity of frequent 
snuflSng, wicks are sometimes so plaited and twisted, or are so slender 
that they bend over to the side of the flame, and coming in contact 
with the air are consumed (Fig. 48). This however is only practicable 
with the more infusible candles, stearine, wax, and spermaceti. Tallow 
melts so easily, that if the wick were bent over, the candle would melt 
down on that side and burn badly. 

200. Influence of the melting point. — Tallow melts at 100°, spermaceti 
at 112°, stearine at 120°, stearic acid at 1G7°, and bleached wax at 
155°. Candles made from those materials which are most infusible of 
course melt slowest ; the liquid which is formed in the cup being smaller 
in quantity may be drawn upward to the flame with a smaller wick. 
Hence the wicks of wax and spermaceti candles are smaller than those 
used for tallow. A slender wick in a tallow candle would melt the 



112 PEODUCTION OF ABTTPICIAX LIGHT. 

combustible faster than it could consume it, the liquid would overfill 
and overflow the cup, which takes place in what is called the guttering 
of candles. For this reason candles of softer materials require larger 
wicks. 

3. Illumination by means of Liquids. 

201. Argand's great Improvement. — Lamps are vessels of various 
forms and appearances for burning light- producing substances in the 
liquid condition. They generally have wicks to feed the flame, which 
may be either solid round masses of fibre like those of the candle, or 
fibres arranged flatwise so as to produce a long thin flame, or they 
may be circular. Dr. Franklin showed that tw"© small wicks placed 
in two candles and burnt side by side, will give more light than if they 
were combined and placed in one candle, as there is a greater burning 
surface ; hence the advantage of spreading the wick-fibres out, and 
using them in some other form than condensed in a solid mass. Very 
large wicks of this kind convert the oil into gas faster than the air can 
completely burn it, and the consequence is that the flame smokes. To 
remedy this evil, the most important improvement yet made in lamps 
was contrived in the year 1789 by Ami Aegand of Geneva, and since 
called after him the " Argand Burner." He made the wick hollow, 
so as to burn in a ring or circle, and thus admitted a current of air to 
the inside of the flame, by which the central core ot dark nnburnt 
gases is avoided, and a double burning surface secured. By means of 
sheet-iron chimneys set above the flame (which were soon replaced by 
those of glass), a strong upward draught of air was secured, which 
heightened the combustion and greatly intensified the light. The 
wick was raised and depressed either by means of cogwork {raclc and 
pinion) or by a screw ; the supply of oil is thus regulated to that of 
the air, and smoking prevented. An important advantage gained by 
the Argand burner is the great steadiness of the light caused by the 
chimney. "When a draught of air strikes an unprotected flame, its 
force and cooling influence check the combustion, and produce flicker- 
ing and smoke. In Argand burners, on the contrary, the supply of- 
air is self-regulated, and the cylinder prevents any interruption of the 
flame by outside currents. 

202. Improvement upon the Argand Burner. — The cylinder that Ae- 
gand employed was straight, or had vertical sides. This allowed a 
much larger amount of air to rise within it than could take part in 
the combustion, and this excess had the partial effect of cooling the 
flame. M. Lange, a Frenchman, improved the form of the chimney- 



ILLUMINATION BY MEANS OF LIQtriDS. 113 

tube, by contracting its size and constructing it with a shoulder at 
such a point (Fig. 51 5), that the rising air striking against it Avas de- 
flected inward and thrown directly upon the flame. This had a power- 
ful efifect in increasing the combustion and heightening the intensity 
of the light. Another improvement consisted in mounting a button 
just above the circular opening within the burner, so that the current 
of air that comes up from within, will be deflected outwards, as shown 
in flg. 54 «, ana thus strike directly upon the inner surface of the 
flame. The main point to be considered in the structure 
and management of lamps upon the Argand principle, or 
with chimneys, is the relation between the current of air 
and the flow of oil. This is controlled by the movable 
wick, the movable button, and the width and height of 
the chimney. As chimneys of glass only can be used, ^--~-' 
they are apt to be made large to lessen the liability to .^^J 
fracture, though the danger is generally overrated. As I™ 

a consequence more air is conducted to the flame than is 
demanded for vivid combustion, while the excess, by rapidly convey- 
ing away the heat, lowers the temperature of the flame, and thus 
diminishes its luminous intensity. Dashing a surplus of air against 
the flame is also unfiivorable to that successive combustion which is 
essential to illumination (192). 

203. Points to be secured in the strnctnrc of Lamps. — Lamps are made 
in a great variety of Avays suited to burn different kinds of oily matter, 
and adapted to avoid, as far as possible, certain difSculties which are 
incident to this mode of lighting. The distance from the burning 
part of the wick to the surface of the reservoir from which the oil is 
derived should remain unchanged, so that an equal quantity of oil 
may be drawn up at all times, and the reservoir should be so shaped 
and j)laced that its shadow will occasion the least inconvenience. If 
the wick is supplied fi-om a reservoir below, it is obvious that just in 
proportion as that is exhausted, the distance from its surfiice to the 
flame is increased ; the wick-fibres elevate less oil, and the light grows 
faint and dim. To remedy this, the reservoir in some cases is made 
to have a large surface of oil that will fall but little distance, although 
a considerable amount is withdrawn. To avoid the objectionable 
shade thrown by such a large cistern close to the wick, tlie astral 
lamp had its reservoir constructed in the form of a narrow circular 
vessel or ring, which threw but a small shadow. The sinumbra lamps 
had this ring so shaped and mounted as to produce still less shade. 
Sometimes there is a fountain of oil placed on one side higher than 



114 PRODUCTION OF ARTIFICIAL LIGHT. 

the wick, with a self-acting arrangement by which the reservoir is fed 
fi'om it, and its height constantly maintained at the same point. The 
shadow cast, in this case^ npon one side, is objectionable, and limits its 
use to that of a study lamp (Fig. 67). In the Oarcel lamp, or mechani- 
cal lamp, clockwork is applied to pump up the oil through tubes in a 
constant stream to the wick, thus keeping it thoroughly soaked, while 
the excess of the oil drops back into the cistern, which is situated so 
far below as to cast no shade. It is moved by a spring, and wound 
up like a clock. It runs six or eight hours, maintaining a constant and 
equal flow of oil, and a bright and steady flame. These lamps are ex- 
cellent, but expensive, costing from fifteen to seventy-five dollars, and 
requiring mach care. 

204. Hot-Oil Lamps. — One great obstacle to the use of lamps lies in 
the viscidity, or thickness and consequent sluggish supply of the oil to 
the wick ; this becomes a very serious difficulty with common lamps 
during the winter. Dr. Uee made some experiments to ascertain the 
relative viscidity or fluidity of difl'erent liquids, and of the same liquids 
at diflerent temperatures. lie introduced 2,000 water-grain measures 
of the liquid to be tested in a cup, and then drew it oflF with a glass 
syphon of \ inch bore, having the inner leg 3, and the outer one 3|- 
inches long. If the weight or specific gravity of two liquids, and 
their consequent pressure upon the syphon were the same, their dif- 
ference of viscidity would be determined by the different time they 
would require to flow off through the tube. He found that 2,000 
grain-measures of water at 60° ran otf through the syphon in 73 sec- 
onds ; but when heated to 180°, they ran off in 61 seconds. Oil of 
turpentine and sperm oil have very nearly the same specific gravity ; 
yet 2,000 grain-measures of oil of turpentine ran off in 95 seconds, 
while that quantity of sperm oil took 2,700 seconds, being in the ratio 
of 1 to 28| ; so that the fluidity of oil of turpentine is 28 J- times greater 
than that of sperm oil. Sperm oil, when heated to 265°, ran off in 
SOO seconds, or one-ninth of the time it took at a temperature of 64°. 
Hence lamps have been advantageously constructed to heat the oil 
before burning, either by means of a copper tube which receives heat 
from the flame, and conducts it downward to the reservoir, or stiU 
better by means of a cistern placed above the flame. Paekee's Eng- 
lish Economic Lamp has its oil heated in this latter way, and is said 
to perform admirably. 

205. Conjpositiou of Oils. — The oils in general use in these lamps are 
those derived from fish, chiefly whales, and known as sperm-oil and 
train-oil. Lard-oil is also much employed. It is the more oily portion 



ILLUMINATION BY HrEANS OF LIQUIDS. 115 

of hogs'-fat separated by artificial means. Tlie chemical composition 
of these oils is quite similar to that of the harder substances which 
are wrought into candles. Sperm-oil consists in 100 parts — of carbon 
78, hydrogen 12, and oxygen 10 ; mutton tallow, of carbon 78-10, 
hydrogen 11-70, and oxygen 2-30 ; wax, of carbon 80-4, hydrogen 
11-3, and oxygen 8-3. 

206. Properties of Spirits of Turpentine or Campliene. — In addition to 
these substances a new class of compounds, the basis of which is de- 
rived from the turpentine of the pine tree, have latterly come into use. 
By distillation of the turpentine pitch, it is separated into a thin trans- 
I)arent liquid, spirits of turpentine or oil of turpentine, and a hard 
brittle residue knowr as common resin. The crude spirits of turpen- 
tine when rectified, that is, separated as completely as possible from 
resinous matter by repeated distillation, is burnt in lamps under the 
name of camphene. It differs from the substances just mentioned in 
its extreme liquidity (being, as we have seen, 283 times more fluid 
than sperm oil) ; in its powerful pungent odor, and in chemical compo- 
sition, as it contains no oxygen, and consists of 88-46 parts in a hun- 
dred of carbon to 11-54 of hydrogen, and is therefore called hydro- 
carhon. Oil of turpentine is also much more highly inflammable, and 
is volatile and explosive. 

207. Conditions required for its Combustion. — Oil of turpentine is a 
superior illuminating substance, but it contains so large a proportion 
of carbon, that if burned in the ordinary way, it smokes excessively. 
Lamps designed to burn it require to be so constructed as to supply to 
the flame a large and powerful draught of air, to effect the complete 
r.ombustion of its elements. Camphene burns with a flame very much 
whiter and brighter than any of the substances we have yet noticed, 
and which displays the natural colors of objects, as flowers or pictures 
in their true tints, much more perfectly than the light of candles and 
oil lamps. Although more luminous, the camphene flame is smaller 
than the oil flame. This is explained by the fact that camphene con- 
sists entirely of carbon and hydrogen, while the fat oils contain 10 
per cent, of oxygen. This oxygen, already existing in the oil, neu- 
tralizes a portion of its carbon and hydrogen, so that there is really 
but 85 or 86 per cent, of hydro-carbon to sustain the combustion ; and 
not only this, but the other 15 per cent, of incombustible matter acts 
to hinder the combustion. On the other hand, the oil of turpentine 
consists of pure combustible matter, burns entirely, and contains 
nothing to retard the activity of the burning process. A hundred 
parts of fat-oil consume only 287 parts of atmospheric oxygon, while 



116 PKODUCnONS OF ARTIFICIAL LIGHT. 

100 parts of camphene consume 328 of oxygen. From its extreme 
fluidity, the oil of turpentine is also supplied copiously and constantly 
to the tlame by the simple capillary or sucking action of the wick. 

208. Why Camphene soon spoils. — Camphene, if exposed to the air, 
cannot be preserved pure. It belongs to a class of bodies known as 
essential oils, which by combination with oxygen are changed into 
substances of a resinous nature. Under the influence of oxygen, oil 
of turpentine undergoes this change, and becomes deteriorated by 
solid resinous impurities. When employed for illumination, therefore 
vt should be procured in small quantities fresh from the manufacturer. 

209. Natnre and properties of Burning Fluids. — There is anothei 
method by which oil of turpentine may be employed.for illumination, 
which is generally much preferred, as it avoids the liability and trou- 
ble of smoke. It consists in mixing it with alcohol, so as to form 
what is known as durninff fluid. Alcohol burned alone produces only 
a feeble bluish-white light, as it is deficient in the necessary quantity 
of carbon. It has the opposite defect of oil of turpentine, as that has 
too much carbon ; the alcohol has an excess of hydrogen. By mixing 
them, a compound is formed which supplies the deficiencies of both, 
yields a good light, and may be burned in lamps of the simplest con- 
struction. These mixtures are commonly burned with wicks, but 
there is a lamp so made that the liquid is vaporized by the heat of the 
burner, and escaping in jets through minute orifices, is burned without 
a wick, like common illuminating gas. Owing to the large propor- 
tion of expensive alcohol which must be used in making it, and which 
gives but very little light, burning fluid is a very costly source of illu- 
mination (230). 

210. In what way Burning Fluids are Explosive. — Both alcohol and oil 
of turpentine are very volatile ; that is, when exposed to the air or 
not confined, they rapidly evaporate or rise into the gaseous state. In 
a lamp reservoir containing burning fluid, as it is gradually consumed, 
vapor rises from its surface and fills the upper space. In all vessels, 
whether lamps, cans, or jugs, if but partially filled with fluid, the re- 
maining space is occupied with its vapor, which may or may not be 
mixed with air. Or when exposed to the air in open vessels, vapor 
rises and charges the atmosphere immediately above. Now the liquid 
oil of turpentine and alcohol are both infinitely more inflammable than 
the fat oils. These cannot be set fire to at common temperatures ; 
they must be heated very hot before they wiU catch fire. But the 
more volatUe liquids, on the contrary, will take fire at any time 
when exposed, though cold, and bum with great violence. But the 



ILLUMINATION BY MEANS OF LIQUIDS. 117 

case is made much worse on account of the invisible vapor which they 
exhale. This mixes with the air, and at the approach of the slightest 
spark or flame, ignites explosively. When pure hydrogen is mixed 
with the air and ignited, it explodes with a sharp report like a pistol ; 
the cause is the sudden combination of the hydrogen with the oxygen 
of the air. Now when vapor of turpentine or alcohol, or any volatile 
hydro-carbon is mingled with air and fired, an explosion takes place 
in the same way. 

211. Conditions under which Explosions occur.— The burning fluid 
itself^ although excessively inflammable, is not explosive. It does not 
go off like gunpowder when set on fire, nor with a sudden noise or 
report, such as its vapor produces. But it is always accompanied by 
the invisible treacherous gas which catches fire at a distance, and this 
ignites the fluid. Most accidents that occur with these compounds 
result from attempts to fill or replenish lamps wliile they are lit, or 
where there is a light near by. Tlie vapor of the opened lamp, jug or 
can, is fired ; it explodes with more or less violence and concussion, 
setting the liquid on fire, and perhaps scattering it upon the clothing 
of the person present, who is severely or fatally burned, while the 
house is very liable to be set on fire. If the lamp have a screw cap 
and be perfectly tight, heat may be conducted downwards from tlie 
fiame througl> tbe metal, and increase the evaporation. There being 
no vent but through the interstices of the wick-threads, if these are 
close, the pressure will increase and force out the fluid and vapor so 
as to burn irregularly, and sometimes occasion little explosions in the 
flame. If the wick is loose, and the lamp be agitated so as to dash 
the liquid against the hot screw-cap, vapor is suddenly formed, and 
being pressed out the flame streams up, often producing alarm. If the 
pressure become too great, and there be no vent, the lamp may ex- 
plode. Dr. Hats says, it is a uniform result of numerous trials con- 
nected with experiments on closed lamps, that no lamp is safe which 
has a closed cap, unless there are openings for the escape of vapor. 
It would be wise to substitute metallic lamps for those of glass, on 
account of the danger of fracture. When these substances are em- 
ployed for light, they should not be committed to the charge of those 
ignorant of their properties ; and it is the only safe rule, when they 
are used in ordinary lamps, never to open any vessel containing them 
when there are lights burning near by. 

212. now Burning Fluids maybe used with safety— Newcll's Lamps. — 
The advantage which these liquids have over oils and candles in re- 
spect of simplicity, cleanliness, and greater brilliancy of light, makes 



118 



PRODUCTION OF ARTIFICIAL LIGHT. 



Fig. 52. 



it eminently desirable that some safe way be devised to consume them. 
This has been done by Mr. John Newell, by applying to them the 
principle of Davy's Safety Lamp. Hydro-carbon gases are often, 
generated in coal mines, and when mixed with common air, are 
exploded by the lamp which the miners use. By surrounding these 
lamps with fine wire-gauze, they could be lit and carried into the dan- 
gerous mixtures without exploding them. The inside of the gauze 
would be fiUed. with burning gas, but the fine wire texture has the 
eff'ect of cooling the flame, so that it cannot pass through and ignite 
the gases outside. Hence, by ingeniously mounting his lamps with 
this gauze, Mr. Newell prevents the possibility of explosion from 
camphene and burning fluids. The can also for contitining the fluid 
has a sheet of the gauze inserted under the lid, and another fixed in 
the spout. These do not prevent pouring; but if vapor or fluid 
escaping through them were lit, the flame could not enter the 
vessel. 

213. Kerosene Oil as au Illumiiiator. — This is a 
product of the distillation of bituminous coal, 
and has come lately into use as a source of 
light. It is rich in carbon, and requires to be 
burned in peculiar lamps adapted to its properties, 
It produces a bright and beautiful light, which 
we have used with much satisfaction. It does not 
vaporize, and is therefore not explosive. The 
proprietors make large claims on the score of its 
economy (230), and are entitled to credit for hav- 
ing prepared a variety of elegant lamps for burning 
it. Fig. 52 represents one of their style of parlor 
lamps. The cistern is narrow, and so far below 
the wick as to cast but little shadow. When not 
burning, the oil emits a kind of empyreumatic gas- 
odor, to Avhich many object ; but the smell is net 
perceived during combustion. 

214. LIglit from SyMc Oil. — This is a cheap oil 
from resin. It gives a vivid light, but it contains 
so much carbon that it is difficult to burn it with- 
out smoking; this may, however, be done with 

Arga^ampfor Kero- Vm^^^' care in VaN BEXSCnOTEN's lamp. 
Bene Oil. 




ILLUMINATION BY MEANS OP GASES. 119 

4. iLLUMINATIOlSr BY GaSES. 

215. Conditions of tlie Gas Manufacture. — The last source of illumi- 
nation to be noticed is gas, which gives the cheapest and brightest of 
all the generally employed artificial lights. It has come into use en- 
tirely within the present century, and has been very widely adopted 
in cities. It was first employed in London in 1802, and its use has 
extended until 408,000 tons of coal have been consumed in a single 
year by the establishments of that city alone ; producing four thou- 
sand millions of cubic feet of gas, and yielding an amount of light 
equal to that which would be produced by eight thousand millions of 
tallow candles, of six to the pound. How wonderful, that sunbeams 
absorbed by vegetation in the primordial ages of the earth's liistory, 
and buried in its depths as vegetable fossils through immeasurable eras 
of time, until system upon system of slowly-formed rocks have been 
piled above, should come forth at last at the disenchanting beck of 
science, and turn the night of civUized man into day. 

210. Materials used for making it.— Gas is chiefly produced from the 
bituminous varieties of coal (87), those which are rich in the pitchy 
elements containing hydrogen. It is also made from tar, resin, oUs, 
fats, and wood. 

217. Products of tlie distillation of Coal. — If coal is used, it is placed 
in tight cast-iron vessels called retorts, which are fixed in furnaces and 
heated to redness by an external fire. The high heat decomposes the 
enclosed coal, producing numerous gaseous and liquid compounds. 
The principal products of this destructive distillation are cohe, or the 
solid residue of the coal, a black oily liquid known as coal-tar ; water 
or steam, various compounds of ammonia, among others that with 
gul2)JiU7'Otig acid, sulphuretted Tiydrogen, carbonic acid and carionic 
oxide, light carluretted hydrogen, heavy carluretted hydrogen or 
olefiant gas, and a small proportion of vapor of sulphuret of carlon. 
There are also variable traces of many other substances. 

218. Purification of the Gas. — This heterogeneous mixture is totally 
unfit for illuminating purposes until purified. The liquid and gaseous 
products, as they are set free, flow out from the retort througli a tube 
into a receiver called the hydraulic main, in which the liquid products 
of the distillation — coal-tar and ammoniacal liquor — are to a great 
extent separated from the gaseous products. But being hot they still 
retain various matters in a vaporous state, which would be deposited 
and clog the pipes ; these are still farther separated by passing tlirough 
the condenser, which consists of iron tubes surrounded by cold water. 



120 PRODUCTION OF ARTIFICIAL, LIGHT. 

The gas is then passed through a mixture of lime and water (milk of 
lime), or through layers of damp slacked lime, which absorb the car- 
bonic acid and sulphuretted hydrogen. It is then sometimes freely 
washed with water, which removes all its ammonia, when it passes 
into a large receiving vessel, the gasometer^ from whence it is dis- 
tributed in pipes to the places where it is to be consumed. 

219. Composition of Illuminating Gas. — This is very variable, but it 
mainly consists of olefiant gas, light carburetted hydrogen, carbonic 
oxide, with free nitrogen and hydrogen, and sometimes other substan- 
ces in small amounts. It takes its value from the proportion of olefiant 
gas which it contains, as this is the chief light-producing compound. 
Olefiant gas consists of 86'21 per cent, carbon to 14'79 per cent, hy- 
drogen. Several other substances which burn with much light are 
liable to be associated with olefiant gas, as Butylene, Propylene, vapor 
of Benzole and Naphtha. Olefiant gas bi;rns with a white and re- 
markably luminous flame ; but it would hardly answer to burn it alone, 
as its proportion of carbon is so large, that if the combustion were at 
all imperfect, there would be liability to smoke. Light carburetted 
hydrogen is the same as the marsh gas, which is generated in the 
organic mud of stagnant pools, and rises upward in bubbles. It con- 
tains less carbon, and is richer in hydrogen ; its composition being 75 
per cent, of the former to 25 of the latter. It burns with a dim yel- 
low flame, giving but little light. Carbonic oxide and hydrogen both 
burn with a fiiint blue, hardly luminous flame. Nitrogen takes no 
part in the burning process, except to hinder it by diluting the gas, an 
effect which is also produced by both carbonic, oxide, and hydrogen. 
The gas that comes off from a charge of good coals consists, when the 
retort is first raised to a vivid cherry-red heat, of 18 per cent, of ole- 
fiant gas, 82-5 carburetted hydrogen, 3-2 carbonic oxide, and 1-3 of 
nitrogen. After five hours the gas that continued to escape gave 7 
per cent, of olefiant gas, 56 of carbui-etted hydrogen, 11 of carbonic 
oxide, 21*3 of hydrogen, and 4-7 of nitrogen. Towards the end of the 
operation, or after about ten hours, it contained 20 parts of carburetted 
hydrogen, 10 parts of carbonic oxide, 60 of hydrogen, and 10 of nitro- 
gen. The best gas therefore is that which is produced first. 

220. Gas derived from other sources. — Crude and refuse oil, which is 
unfit for burning, is sometimes converted into gas. It is made to 
trickle into a retort, containing fragments of coke or bricks heated to 
redness. The oil, as it falls upon tliese fragments, is instantly decom- 
posed and changed to gas. It contains no sulphur products, and needs 
no purification. It is very rich in olefiant gas, and has double the 



ILLUMINATION BY MEANS OF GAS. 



121 



Fia. 58. 



illuminating power of the best coal gas, and treble that of ordinary 
coal gas. Eesin ako, by being melted and treated in a similar way, 
yields a highly illuminating gas. But in point of economy, neither oil 
nor resin can compete with coal as a source of light. A pound of coal 
yields from three to four cubic feet of gas ; a pound of oil, 15 cubic 
feet ; of tar, 12 ; and of resin, 10. 

221. How Gas is measured. — Gas is sold by the cubic foot, or by the 
thousand cubic feet. From the underground pipes (mains) that run 
through the street, a pipe branches off leading to the dwelling to be 
illuminated. Before being distributed through the house the gas I3 
made to pass through a self-acting instrument called a meter, which 
both measures and records the quantity consumed in a dwelling. The 
meter consists of an outer stationary cylindrical case, enclosing an 
inner and smaller cylinder which revolves upon its axis. Both cylin- 
ders are closed at the ends, water-tight and gas-tight. The inner one 
is divided into four compartments with crooked partitions, and the 
gaspipe passes into its centre or axis, and, turning up at the end, do- 
livers to them its contents successively. The meter is kept about two- 
thirds filled with water, which the gas 
constantly displaces as the cylinder turns. 
The principle will be understood by the 
aid of the diagram (Fig. 53), which ex- 
hibits the meter as if seen endwise, with 
the ends of the drums removed. A A A A 
is the outer cylinder ; B B B B the four 
compartments of the inner one ; c is the 
gaspipe supplying one of the apartments. 
Ai it enters the partition E rises, and the 
water passes out at the slit i?, into the 
space between the two cylinders. The in- 
ternal one revolves from left to right, the 
gas passing in the direction of the arrows, 
first displacing the water and filling the compartments, and then 
passing out into the space between the two drums, where it is con- 
veyed away by a tube not shown in the figure. The revolving drum 
is connected with clockwork, which shows by an index the number 
of revolutions made, and the capacity of the compartments being 
known, the quantity of gas which passes through is correctly deter- 
mined. The meter reports the amount of gas that actually passes 
through it ; but its indications are by no means to be taken as infalli- 
Dle proofs of honesty on the part of the gas company. Their tompta- 
6 




Meter for measuring the flow of 

Gas. 



122 PRODUCTIONS OF ARTIFICIAL LIGHT. 

tion is, to put on pressure aud crowd more gas through than is neces*- 
sary, or than can be burned with economy, for inereased consumption 
of gas does not at aU involve a corresponding increase of light (222). 
Nor do meters afford any indication whatever in reference to the 
quality of the gas ; the companies control this, and may do quite as 
they please, the customer being unprotected. We do not intimate, 
however, that the gas-companies ever yield to the evil temptations 
with which they are beset. 

222. How Gas is burned. — From the fountain of distribution — the 
gasometer — the gas flows away through the branching system of tubes 
under the influence of pressure. When little openings are made in 
the pipes, this pressure drives out the gas in jets or streams, and it is 
these which produce the light when ignited. The orifices are from 
Jifth to the -^^ih of an inch in diameter. Eecent experiments by the 
French tend to show that wider openings are more economical with 
the best kinds of gas. The openings are made in various ways. A 
circle of them round a large central orifice forms an Argand burner 
(201). Two holes drilled obliquely, so that the flames cross each other, 
produce what is called a swallow-tail jet. A slit gives a continuous 
sheet of flame, called a hat-wing jet. Other figures are also produced, 
as the '•'■fan-jet,'''' '■'■fish-tail jet^'''' &c. The quality of light depends much 
upon the mode of burning as well as the composition of the gas ; a 
good article may be spoiled by mismanagement. Its illuminating 
power is impaired when burned too rapidly to allow the separation 
and ignition of the carbon particles (190). The order of the combus- 
tion, upon which aU illumination depends, is destroyed, by excess of 
air, as when we move a lighted candle rapidly through the atmosphere, 
the hydrogen and carbon are both burned at once, and we get only a 
feeble blue flame. This occurs Avhen gas issues with considerable ve- 
locity from a minute orifice, and by expansion gets intimately mixed 
with a large proportion of air. When the current of gas does not 
ignite at a considerable distance (several lines) from the aperture, 
aud then burns with a faint blue flame, the gas-stream is too rapid, it 
is improperly mingled with the air and consumes wastefuUy, — that is, 
to the iuyer. If chimneys are used, and the draught becomes too 
strong, for the same reason the light almost vanishes, yielding only a 
dull blue flame. On the other hand, too small a draught of air is 
equally injurious, not only from incomplete combustion which causes 
the flame to smoke, but also because the highest illuminating power 
of the flame is obtained only when the carbon atoms are heated to 
whiteness, which requires a considerable amount of air. We have 



ILLUMINATION BY MEANS OF GAS. 123 

before seen how rapidly light is evolved hy the addition of small 
quantities of heat at high temperatures (188). 

223. Iiiflaencc of the length of the Flame. — The dimensions of the gas- 
flame may be controlled with perfect facility by simply turning a stop- 
cock, although its extent depends upon the width of the orifice and 
the amount of pressure. It was found that if the light from a flame 
2 inches long were represented at 100, at 3 inches it became 109, at 
4 inches 131, at 5 inches 150, at 6 inches 160, with an equal consump- 
tion of gas in each case. 

224. How much, Gas-bnrning contaminates the Air. — The active source 
of light in this kind of illumination, as has been stated, is olefiant gas 
and other compounds abounding in carbon. But these could not be 
burned alone even if it were possible to procure them. A diluting 
material is therefore necessary to give the flame sufficient bulk, and 
separate the particles of carbon so far asunder as to prevent the risk 
of imperfect combustion and smoke. Now the three substances found 
in gas — light carburetted hydrogen, carbonic oxide, and free hydi-o- 
gen — are all equally well adapted for this purpose. So far as light is 
concerned, it is of little consequence which of these is associated with 
the olefiant gas. But in other respects this becomes a matter of im- 
portance. The two objections most commonly urged against the use 
of gas in our apartments are, first^ the heat which it communicates to 
the air ; and, second^ the contamination of it by carbonic acid. Now, in 
these particulars, the three diluting substances have very different in- 
fluences. One cubic foot of light carburetted hydrogen consumes in 
its combustion two cubic feet of oxygen, and generates one cubic foot 
of carbonic acid, — a portion of the oxygen being consumed in the for- 
mation of water with hydrogen. This produces a sufficient amount 
of heat, according to Dr. Feankland, to raise 2,500 feet of air from 
60° to 80-8°, while a cubic foot of hydrogen burned under the same 
circumstances produces no carbonic acid, and yields heat capable of 
raising 2,500 cubic feet of air 60° to 66*4°. One cubic foot of carbonic 
oxide consumes in burning half a cubic foot of oxygen, and generates 
one cubic foot of carbonic acid. The light carburetted hydrogen, 
therefore, is the worst diluent and hydrogen the best, as it produces 
no carbonic acid, and excites least heat. We saw that at different 
stages of heating, the coals in the retort yielded at one time a gas, rich 
in illuminating constituents, and at another time a gas deficient in 
these, but rich in hydrogen (216). Advantage has been taken of this 
fact to mingle the products of the retorts at different stages of heat- 
ing, by which the olefiant gas is diluted with hydrogen, and a mixture 



124 PEODUCTIONS OF ARTIFICIAL LIGHT. 

produced of superior iUuminating qualities and the least injurioug 
effects. 

225. Disadvantages of Gas-lighting. — The chief obstacle to the use of 
gas-lights in private houses is, that the burners are stationary, and 
cannot be placed in positions available for all purposes. Candles and 
lamps are movable, but a gas-light, even where flexible india-rubber 
tubes are used, is more or less a fixture. The burners being usually 
situated high for general illumination, and calculated for giving more 
light than is required for one or two persons, cannot be reduced to the 
limits of the strictest economy of consumption. Hence, although gas 
is the cheapest of all sources of illumination, this apparent necessity 
for consuming it in large quantities prevents the real saving that might 
otherwise be expected. We have just spoken of the effects of burning 
gas upon the air, and shall notice it again, as also the prejudices against 
its use (275). 

226. Care of Gas-fixtares. — Air, when mixed with gas, exerts upon 
it a slow change, tending to produce fluid and solid bituminous bodies 
by oxidation. Now if air gets access to the tubes and mingles with 
the gas, as it does constantly between the burner and the stop-cock, 
when the gas is not burning, the pipe becomes coated and obstructed, 
and hence requires periodical cleaning, which should be done with in- 
struments that ought to be furnished gratuitously by the gas com- 
panies. Gas of high value contains six per cent, of its volume in 
vapor, which can become fluid in the pipes when they are exposed to 
the temperature of freezing water. Hence depressions in the pipes 
soon collect fluids, unless they decline towards instead oi from the 
meter, and the flow of gas to the burner is irregular, producing fluc- 
tuation or what is called 'jumping' of the flame. When the burners 
are long out of use, as sometimes in summer, the pipes are liable to 
become deranged and clogged, and as gas acts on and solidifies all oily 
and lubricrating substances hitherto used, the keys of stop-cocks of1;en 
become fixed. — Hays. The ventilation of gas-burners will be de- 
scribed when treating of air (360). 

5. Measubement of Light. 

227. Can Liglit be Measnred ? — It is sometimes of importance to de 
termine the cost of light produced in diflerent ways and from difterent 
materials. There is no method known by which light can be directly 
measured ; that is, we have no mode of estimating the absolute quan- 
tity of light emitted by a flame, but we can ascertain how much more 



MODE OF ITS MEASUREMENT. 



125 



Fig. 54. 



or less light one flame produces than another, and thus arrive at useful 
comparative results. All flames are not eqnally hright, — of two flames 
of equal size, one may be much more brilliant and emit more light 
than the other. Wo do not judge of the intensities of different lights 
by direct comparison, but by the comparison of their shadows, on the 
principle that the greater the illuminating power of the light the 
deeper is the shadow which it casts. 

228. How Liglit is Measured. — Before a piece of board, covered with 
unglazed white paper at a distance of two or three inches, let an iron 
rod be placed which has been previously blackened by holding it in 
the candle. Now if it is desired to compare two lights, they are to 
be placed opposite the 
board at the same 
height, and each will 
cast a shadow upon 
the paper as illustra- 
ted in Fig. 54. The 
lights should be so sit- 
uated that the shad- 
ows will fall close to 
each other, and the 
stronger flame should 
be so far removed, or 
the weaker idvinopd Photometer or contrivance for measuring the Intensity of light. 

that both shadows will appear equally deep. To ascertain their 
luminous intensities we measure the difference from their centres to 
the shadow : if these are equal, their illuminating powers are equal ; 
but if one casts an equal shadow at a greater distance than the other, 
its light must be more intense, or its illuminating power greater. The 
difference in the degrees of light is not proportional to the distances 
of the luminaries from their shadows, but to the squares of these dis- 
tances, in accordance with the law of radiation before explained (136). 
If one light at two feet, and another at six, give equal shadows, their 
difference is not as six to two, but as the square of 6, which is 36 to 
the square of 2, which is 4 ; that is, 86 to 4, or 9 to 1. The luminary 
at 6 feet gives nine times as much light as the one at 2 feet. 

229. We have no unit for measuring Light. — This plan, modified in va- 
rious ways, affords a ready means of comparing the relative amount 
of light emitted by two flames. But we have not been able yet to 
reap the practical advantages which this success at first appears to 
promise. If we can measure light, why not establish the exact illurai- 




126 STRUCTUEB AND OPTICAL POWERS OF THE EYE. 

nating values of the various lighting materials, so that we may kiio-w 
precisely how far a dollar will go in buying light when the substances 
are at given prices. Something has been done in this way, but we 
have no results that command implicit trust. The composition of the 
materials is variable, and the same materials in different trials give 
different results. We are without an accepted unit to serve as a stand- 
ard for a scale of values. It has been proposed to make the sperma- 
ceti candle (6 to the lb.), burning 120 grains to the hour, the unit of 
measure. If this were satisfactory, we could compare other lighting 
materials with it. A burner consuming a certain amount of gas per 
hour would equal a given number of candles, and any variation in its 
quality would be easily detected. "We should speak of it as 10 candle- 
gas, 16 candle-gas, and 20 candle-gas, according to its grade, and so 
of tlie various illuminating substances. But these candles have been 
found to burn variably, and do not perfectly answer. Some unit will 
probably be fixed upon by which the comparative values of lighting 
materials may be determined and expressed. 

230. PUctonictric Results of Ure and Kent.. — Dr. Uee gives the follow- 
ing as the cost of an equal amount of light per hour from several 
sources, according to his experiments. 

Ponce. 

Carcel Lamp, with Sperm Oil 1 J 

Wax Candles 6 

Spermaceti Candles 6i 

Stearic Acid Candles 4j 

Moulded Tallow Candles 2\ 

E. N. Kent, of the U. S. Assay Office, experimented on various 
lighting materials with the following results : 

Retell price of Cott of an equal 

MflteriftU. Lamp used. Oil per gallon. amount of light. 

Kerosene Oil Kerosene $1 00 $4 10 

Campbene Camphene 63 4 85 

Sylvic Oil .-. Rosin Oil 60 6 05 

Rape Seed Oil Mechanical 1 5ft 9 00 

Whale Oil Solar 1 GO 12 00 

Lard Oil Solar 1 25 17 00 

Sperm Oil Solar 2 25 26 00 

Burning Fluid Large Wick 87 29 00 

VIII.— STRUCTUEE AND OPTICAL POWERS OF THE EYE. 

231. Yalne of the sense of Vision. — The eye is perhaps the most im- 
portant organ of sense. By it the mind is put into the widest com- 
munication with the external world. Although it may be said that 
this organ only recognizes light and colors, yet through it we become 
acquainted with the forms, magnitudes, motions, distances, directions 
and positions of aU objects, whether immediately around us, or re- 



THE IRIS AND PUPIL, AND THEIR USES. 127 

motely distributed tlirough the distant universe. In its adaptation to 
the agent wbich is designed to act upon it, the eye is a miracle of 
beauty and wise design. For this reason alone we might well afForc' 
to devote a little space to it ; but when we consider that it is an organ 
of exquisite delicacy, and greatly liable to abuse from the domestic 
mismanagement of light, as well as other causes, and remember how 
tedious and distressing are its disoi-ders, and what a lamentable life- 
disaster is its loss, it becomes of the first importance to assist in diffus- 
ing any suggestions that may lead to its better care. Our previous 
study of light and colors will moreover aid us materially in forming 
correct ideas upon the subject. 

232. Sclerotic Coat and Cornea, and their nses. — When the eye is re- 
moved from its socket and dissected, it is found to consist of several 
coats. The outer one forms the whlt^ of the eye ; it is a tough, re- 
sisting membrane, and serves both to sustain the delicate parts within, 
and also to give insertion to those outer muscles which i-oU the eye- 
ball. It is called the sclerotic coat^ or briefly the sclerotic. As light 
is to enter the eye, and as, from the nature of the organ, it could not 
be admitted through a hole, it became necessary to have a window in 
the eye-ball. In the front part of the globe there is a circular open- 
ing in the sclerotic, which is closed by a thin and perfectly transparent 
membrane called the cornea, the front window of the structure. The 
cornea bulges out somewhat like a Avatch-glass ; that is, it is more 
convex than the general surface of the eye-ball, Si may be felt through 
the closed lid. It covers that portion of the eye i\ Inch is colored, and 
is attached round the edge of the colored part to the sclerotic coat, 
with which it is continuous. The cornea is very hard, tough and 
horn-like, the word being derived from the Latin cornu, which signi- 
fies ?iorn. The general arrangement of the parts we are describing is 
shown in the accompanying view of the section of the eye (Fig. 55). 

233. The Iris and Papil, and their uses. — Behind the cornea 
there is a small space or chamber filled with a perfectly clear and col- 
orless liquid, which consists chiefly of pure water, and is called the 
aqueous humor. This chamber is divided by a thin partition known 
as the iris, in the centre of which there is a circular aperture called 
the pupil. The pupil is simply, therefore, a hole through the iris ; it 
is the round black sj^ot which we see surrounded by a colored ring. 
That colored ring is the iris. It is black behind, and on tlio front 
or visible side, it is of different colors in different individuala. The 
color of the iris is observed to be, in some measure, connected with 
the color of the hair. The iris has the remarkable property of con- 



128 



STEUCTUEE AKD OPTICAL POWEES OF THE EYE. 




Vitrecus 

hitmoiLr 
Ch oroii 
> coat 

Retina 



Cornea, 



tracting and dilating under the influence of light, by which the pupU 
is enlarged and diujinished. If the light he strong, the iris contracta 
and reduces the size of the pupil, so as to exclude a portion of the 

light ; if the light he weak, the iris 
expands so that more light is ad- 
mitted. This moderates and equal- 
izes the illumination of the organ, 
the delicate sensihility of which 
might otherwise be injured. The 
play of this mechanism may easily 
be seen by bringing a candle near to 
the eye while gazing upon its im- 
Eelation and names of the several parts age in a looking-glass. These move- 
of the Eye. ments are involuntary, the eye reg- 

ulating the quantity of light it will receive, independent of the choice 
of the mind. 

234. Crystalliue Lens and Vitreous Humor. — Behind the little chamber, 
of which we have spoken, and bounding it on the back side, is a sub- 
stance in the form of a double convex lens, called the crystalline lens. 
It is situated immediately behind the pupil, very near it, is a little 
larger than that opening, and is very convex, its thickness being al- 
most equal to its diameter. It is supported by a ring of muscles called 
the ciliary process. The crystalline has about the consistence of hard 
jelly, and is purer and more transparent than the finest rock-crystal. 
It is this part which becomes diseased in cataract. The space behind 
the crystalline lens constitutes the main body of the eyeball, and 
is filled with a clear gelatinous fluid, very much resembling the white 
of egg, and called, from its apparent similarity to melted glass, the 
vitreous humor. 

235. The Choroid Goat, and how it is Colored. — There is a second coat, 
lining the interior of the sclerotic, which consists of minute vessels, 
arteries, and veins, closely internetted, and is called the choroid. It 
extends around to the cornea, and supports the ciliary process. The 
inside of the choroid is covered with a slimy matter of an intensely 
black color, called the pigmentum nigrum (blacTc pigment). This 
gives to the interior of the eye a jet-black surface, which absoi'bs and 
stifles the light, so as effectually to prevent reflection. 

236. Optic Nerve and Retina. — At the back part of the eye, the scle- 
rotic coat is formed into a tube which leads inwards to the brain. 
This tube contains the optic nerve. As it enters the globe, it spreads 
out over the inner surface of the choroid, in the form of a most deli- 



THE RETINA SUPPOSED TO FEEL THE PICTURE. 



129 



Fig. 56. 



cate network of nervous filaments, called, from its reticulated struc- 
ture, the retina. The retina is therefore the extended and diffused 
optic nerve. In dissection it is easily separated from the choroid. It 
is absolutely transparent, so that light and colors penetrate and pass 
through it perfectly'', and therefore fall upon the dark surface beneath. 
To prevent the delicate and transparent nerve tissues of the retina 
from being stained by the black pigment, a very thin film is interposed 
between them called JacoVs membrane. 

237. How Vision is Produced. — From every object which we see, 
rays of light pass into the eye, penetrating the successive transparent 
media, the cornea, the aqueous humor, the crystalline lens, and the 
vitreous humor, and falling upon the retina, form there an image of 
the visible object, the impression of which is carried by the optic 
nerve to the brain. 
The diagram (Tig. 
56) shows how, in 
the perfect eye, the 
image is made to 
fall accurately upon 
the retina. It is 
seen to be inverted. 
The pictures in the 
eye, of every thing 
we behold, are upside down, although there is no confusion, and we 
are unconscious of it. We have said that the image is formed upon 
the retina, and this is the common mode of expi'ession, but that is 
perfectly transparent, so that the colored image is formed, not proper- 
ly upon it, but upon the black surface of the choroid coat behind it. 
It is maintained that the retinal membrane is affected by the colored 
image in the same manner that the sense of touch is affected by ex- 
ternal objects. It is supposed to touch or feel, as it were, the image 
on the choroid, and transmit the impression to the brain, something 
in the same way that the hand of a blind person transmits to the or- 
gan of consciousness, the form of an object which it touches. This 
view seems to be confirmed by the fact, that at that portion of the 
retina where the optic nerve enters the eyeball, which therefore has 
not the black choroid behind, it is insensible, and produces no per- 
ception. It has been proved by experiment that images made to fall 
upon that spot, are instantaneously extinguished. 

238. Wonderful Minuteness and Distinctness of tlie Imagest — Nothing 
is more calculated to awaken our astonishment than the perfect dis- 

6* 




How the Images are formed in the perfect E70. 



130 STBUCTUBE AND OPTICAL POWERS OF THE EYE. 

tinctness of the pictures upon the retina, compared with their magni- 
tude. The diameter of the picture of the full moon upon the retina 
is but the jlo^ part of an inch, and the entire surface of the picture is 
less than the X2W0 P*^^*- ^^ ^ square inch. And yet we are able to 
perceive portions of the moon's disc, whose images upon the retina are 
no more than the 15,000,000th part of a square inch. The figure of a 
man 70 inches high, seen at a distance of 40 feet, produces an image 
upon the retina the height of which is about the j\ part of an inch. 
The face of such an image is included within a circle whose diameter 
is about ~ of the height, and therefore occupies on the retina a cir- 
cle whose diameter is about ^\ part of an inch ; nevertheless, within 
this circle, the eyes, nose, and lineaments are distinctly seen. The 
diameter of the eye is about ~ that of the face, and therefore, though 
perfectly visible, does not occupy upon the retina a space exceeding 
the l-4,000,000th of a square inch. If the retina be the canvas on 
which this exquisite miniature is delineated, how infinitely delicate 
must be its structure, to receive and transmit detaUs so minute, with 
such wondrous precision ; and if, according to the opinion of some, 
the perception of these details be obtained by the retina feeling the 
image formed upon the choroid, how exquisitely sensitive must be its 
touch, (Lardnee.) 

239. Adaptation of the Eye to Intensities of Light. — The susceptibility 
of the eye under great variations of intensity in the light which en- 
ters it, is most wonderful. We can read a book either by the light of 
the sun or of the moon, yet sunlight is more than a quarter of a mil- 
lion times more brilliant than moonlight. "The direct light of the 
sun has been estimated to be equal to that of 5,570 wax candles of 
moderate size, supposed to be placed at the distance of one foot from 
the object. That of the moon is probably only equal to the light of 
one candle at a distance of twelve feet, hence the light of the sun is 
more than 300,000 times greater than that of the moon." Wollaston 
estimated the light from Sirius, one of the largest fixed stars, as twenty 
thousand million times less than that of the sun. 

240. Conditions of the System affect the Eye. — The eye is thus an opti- 
cal contrivance which challenges our wonder continually for the ex- 
quisite beauty and perfection of its parts. Yet we must not forget 
that it is a living organ of the body made up of vessels, membranes, 
muscles and nerves, and nourished by the vital blood-stream like any 
other organ. It is therefore liable to be influenced in numberless 
ways by conditions of the system. When in use, it acts, expends force, 
exhausts itself and becomes fatigued. Dr. Whaeton Jones remarks : 



STATES OF THE BODY AFFECTING THE EYES. 131 

* Much exertion of the ej^es operates more prejudicially to the sight 
under some circumstances than under others. Exertion of the sight 
is especially prejudicial immediately after a full meal; after the use of 
spirituous drinks ; while smokmg ; when the body is in a recumbent or 
stooping posture, when dressed in tight clothing, especially a tight 
neckcloth ; tight corsets ; and even tight boots or shoes ; in close and 
ill-ventilated apartments lit with gas ; after bodily fatigue ; during men- 
tal distress ; late at night when sleepy ; after a sleepless night ; while 
the bowels are much confined ; during convalescence from debilitating 
illness. Though during recovery from severe disease the eyes cannot 
bear much exertion, yet, for want of other employment, it is not un- 
common for convalescents to read even more than when in health. 
Kany persons have much injured their sight in this way. Young 
growing persons, at the age of puberty, persons of weakly constitu- 
tions, are incapable of supporting much exertion of the eyes without 
injury to the sight." Sudden suppression of the perspiratory action 
of the skin, or any cause which determines a pressure of blood to the 
head, is also liable to affect the eyes injuriously. 

241. Reading and Writing. — In this reading age, with such strong 
and insidious temptations to overuse and bad management of the eyes, 
it may be well to make some suggestions concerning this mode of 
exercising vision. The closer the eye is confined to the page, the 
more of course it is strained. Novel reading is worse than science, 
history, or any grave subjects, because in the first instance we read 
fast and uninterruptedly, while in the latter cases thinking alternates 
with the use of the eyes in reading. Reading from a broad page with 
the lines long and the print small, is very tiresome, as it is difficult 
for the eye always to take up the next line. Writing down our own 
thoughts is easy for the sight ; but copying is hard, as we have both 
to read and write, and look backward and forward in addition, 

■ Reading when in motion, as in riding or walking, or in the brightness 
of sunshine, or under a tree, where from the motion of the leaves by 
the wind lights and shadows fly over the page, are all severe upon the 
eyes, and liable to injure them. But perhaps the most serious mischief 
to which we are exposed in reading, comes from the bad quality of 
ailificial light, which we shall notice particularly further on. 

IX.— OPTICAL DEFECTS OF VISION— SPECTACLES. 

242. Limits of perfect Tision. — The transparent portions of the eye, 
the cornea and included humors, act as lenses (149), which bend or 
refract the light from its straight course as.it passes through them, 



132 



OPTICAL DEFECTS OF VISION — SPECTACLES. 



Fig. 57. 



bringing it to a point or focus at the back of the eye. Where the 
vision is perfect, the rays are so bent that the image, in its utmost 
distinctness of outline and color, falls exactly iipon the retina, as shown 
in Fig. 56. If the eye were a fixed or rigid mechanism, as if made 
of glass, only objects at certain precise distances would come to a 
point upon the retina, all others would produce their images either 
before or behind it, and thus give rise to imperfect vision. But the 
organ possesses a power of adjustment by which objects at different 
distances may be seen clearly. How this occurs is not understood. 
Perhaps the crystalline lens is capable of slightly varying in position 
and curvature. The limits of perfect vision in the normal eye vary 
somewhat in different persons ; but in general they may be put down 
as between nine and fifteen inches. 

243. Cause of Far-sightedness.— The eye is a system of lenses beau- 
tifully arranged to bend light to a point. But its bending or con- 
vergent powers may be too liigh or too low, 
producing imperfect vision in either case. 
This converging or refractive power de- 
pends upon the curvature of the lenses 
The rounder they are, the stronger they are ; 
the flatter they are, the weaker they become. 
As persons advance in life, there is a ten- 
dency to loss of fluids, which fill and dis- 
tend the body, and a consequent shrinking 
W of the flesh and wrinkling of the skin. Th( 

Far-sighted Eye with flattened ^y^ participates in this natural change of 
tissue, its contents seem to shrink, and the 
cornea becomes flattened or loses something of its convexity, appear- 
ing as shown in Fig. 5V. This 'profhices far-sightedness^ in which per- 
sons can see objects distinctly only when they are at a very consider- 
able distance from 
the eye, such as 
holding the book 
at arm's length in 
reading. In this 
state of the eye 
the rays tend to a 
focus at a point 

behind the retina, 
Far-sighted Eye — the focal point thrown too far back. ,. ■, fv,p-p 

fore, they strike in a scattered state, forming an indistinct image. In 




Fig. 6S. 




CORRECTION OF FAR-SIGHTED EYES. 133 

Fig. 58 the object a has its focal point thrown back to &, making a 
confused picture upon the retina at c. The further an object is from 
us, the less divergent or more parallel are the rays coming from it ; 
and the less divergent are the rays which enter the eye, the easier are 
they brought to a focus by it. This is the reason that to the far- 
sighted, distant objects are distinct, and near ones confused. The far- 
sighted see minute objects indistinctly at every distance, because when 
near they are out of focus, and when remote from the eye, they do not 
reflect sufficient light to make a strong impression. They hence strive 
to increase the light upon the object, as we often see when attempting 
to read by candlelight, they place the candle between the book and 
the eye, and both at arm's length. It is but rarely that eyes recover 
naturally from this defect, yet much may be done to preserve the 
sight by care. When the eyes begin to fail, all over-exertion, as 
minute work or reading by badly arranged artificial light, should 
be avoided. As soon as the eyes begin to feel fatigued or hot they 
should have rest. 

244. How Glasses help the Far-sighted. — The remedy for this defect 
is convex lenses, which are so selected and adapted to the eye as ex- 
actly to compensate for the want of refracting power in the organ 
itself. These len- j-jq_ ^g 

ses gatlier the rays 
to a point at vari- 
ous distances de- 
pending upon their 
curvature. The 
greater the curve, 
the nearer the fo- 
cus and the higher 
the power • while Far-sighted Eyo corrected by double convex glasses. 

with less curvature, and a more distant focus, there is lower poAver. 
The refractive power of a glass is expressed by the distance of its 
focal point in inches. A 10-inch glass, or a No. 10, collects the rays 
to a point at a distance of 10 inches, a No. 5 at 5 inches, and a No. 
20 at 20 inches. The higlier numbers express the lower powers, and 
the lower numbers the higlier powers. Fig. 59 shows the far-sighted 
eye, with its internal focus, properly adjusted by a convex glass. 

245. Management of far-sighted Eyes. — "When the sight begins to fail, 
and glasses are sought, those of the lowest power, which will bring 
objects within the desired distance, should be chosen. But they 
should be comfortable and not cause headache, nor strain or jfiitigua 




134 OPTICAL DEFECTS OP VISION — SPECTACLES. 

the eyes ; if they do this, they are too convex. If practicable, it is 
well to get two or three pairs from the optician, as nearly correct as 
possible, and try them leisurely at home before deciding which to take. 
If the eyes only see clearly at a very great distance, the No. of the 
glass required will be the same as the number of inches at which it is 
iesired to read. But the moderately far-sighted do not require such 
strong glasses. If they can see small obj ects distinctly at 20 inches 
distance, for example, and wish to be able to read at 12, the power of 
the desired glass may be obtained by multiplying the two distances to- 
gether, and dividing the product, 240, by the difference between them, 
viz. 8 ; the quotient, 30, is the focal length in inches of the glasses re- 
quired. The intensity of the light influences the power of the glasses 
used ; it is commonly found that those a degree more convex are re- 
quired by artificial light, than by daylight. Many suppose that glasses 
of cei'tain focal lengths correspond to certain ages, but no rule of this 
kind is safe. The nearest average relation between the age and the 
focal length of the convex glass is as follows: 

Age in Tears 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90. 

Focal Length in Inches. 36, 30, 24, 20 16, 14, 12, 10, 9, 8, 7. 

246. Near-sightcdncss. — This is the opposite defect ; the cornea is 
too rounded and prominent, as shown in Fig. 60. The rays of hght 
which fall upon it are consequently too powerfully refracted, and ar- 
riving at a focus before reaching the ret- 
ina, cross, and are in a scattered state 
when they do faU upon it, as illustrated 
in Fig. 61, where a is the object, & the 
focus, and c the confused rays falling 
upon the retina. In this condition of 
vision, persons can see objects with per- 
fect distinctness only when they are at a 
short distance from the eyes ; if they 
bring minute objects closer than ten 
Near-sighte'j Eye, w.th its Protrud- inches they are usually accounted near- 
ing Cornea. sighted. By bringing the object nearer 

it is distinctly seen, because the rays of light from It which enter the 
eyes, being more divergent than when it was distant, are not so soon 
brought to a focus. The near-sighted eye retains its power of adjust- 
ment to distances ; the nearest distance may be from 2 to 4 inches, 
while the greatest is from 6 to 12. Short-sighted people see minute 
objects more distinctly than other people, because from their nearnesa 




CORRECTION OF NEAR-SIGHTEDNESS. 



135 




Near-sighted Eye, the focus falling too far forward. 



they are viewed under a larger angle and in stronger liglit. They can 
see better than others with a weak light, and hence can read small 
print with a feeble illumination. To persons who are occupied with 
minute objects, short-sightedness, unless extreme, is rather an advan- 
tage, as they can 
observe all tho 
details of their 
work very ac- 
curately, while 
for distant vis- 
ion they can get 
ready help from 
glasses. Yet if 
an eye be at first 

perfect, the constant employment of it upon small objects tends to 
produce near-sightedness, which is hence a common defect of vision 
among the educated classes, and those who do much minute work. 
On the contrary, the habitual exercise of the eyes upon distant objects 
improves their power in that direction. If young persons have a ten^ 
dency to nearness of sight, and are designed for vocations in which 
lengthened vision is required, they should avoid much exertion of 
the eyes on small objects, and exercise them frequently in scenes in 
the open country. It is an error that the near-sighted acquire perfect 
vision as they advance in life. "We often see old people who are com- 
pelled to use near-sighted glasses ; indeed, this state of the eyes some- 
times occurs in old persons whose vision was previously at the usual 
distance. 

247. Management of Near-sightedness. — Concave glasses extend the 
vision of the near-sighted by separating or diverging the rays of light 
before they enter 
the eye, so that 
they may be less 
quickly brought 
to a focus, and 
the image formed 
further back, as 
shown in Fig. 62. 
The powers of 
glasses for the 



Fio. 62, 




Near-sighted Eye, corrected by double concave glass. 



near-sighted are expressed in a manner contrary to those for the far- 
Kighted (245). They are numbered 1, 2, 3, &c., No. 1 having the 



136 OPTICAL DEFECTS OP VISION — SPECTACLES. 

smallest convexity and the smallest power, and being therefore adapted 
for those that are least near-sighted. In selecting glasses, the near 
sighted should choose the lowest or weakest powers that will answer 
the purpose, and the best plan is to make trial of a series, as was sug- 
gested to the far-sighted. If the glasses make objects appear very 
bright, or glaring, or email, or produce fatigue, strain, or dizziness and 
confusion of vision after being laid aside, they are too concave. If 
glasses are wanted for reading or to behold near objects, the power of 
the required glass may be determined as follows : Let a person multi- 
ply the distance at which he is able to read easily with the naked eye, 
say four inches, by the distance at which he wishes to read, say 12 
inches, and divide the product, 48, by the difference between the two, 
which is 8 ; the quotient, 6, is the focal length of the glasses required. 
The far-sighted have to change their glasses as the sight progressively 
fails, but near-sightedness usually continues much the same through 
the greater part of life, so that the same glass gives assistance a much 
longer time. It is well for both the far-sighted and near-sighted to 
employ glasses of various grades for different purposes. Thus the 
near-sighted need glasses adapted to distant objects, and as they are 
much inclined to stoop in reading and writing, they might remove the 
eye further from the page by using glasses of slight concavity. Near- 
sigh tedness may be occasioned by other causes than the one just no- 
ticed. There may be a declining sensibility of the retina, which makes 
it necessary to bring objects nearer to the eye ; this is called nervous 
short-sightedness, and although objects are seen better close by, yet 
they are not seen so distinctly as in true or optical short-sightedness. 
Such persons seek strong light, to get a more vivid impression, and uso 
convex glasses to increase the light upon the retina. This use of glasses 
is perilous (266). Short-sightedness is sometimes a symptom of com- 
mencing cataract. This disease is not, as is commonly supposed, 
something growing over the sight on the outside of the ball. It is a 
change in tlie crj'stalline lens, by which it loses its transparency, and 
becomes more or less opaque, so as to confuse, scatter, or stop the 
light, and destroy the distinctness of the image. Children often shorten 
their vision at school by stooping over their desks and poring over 
bad print, combined with the debilitating action of extreme heat and 
bad air, a result which should be carefully guarded against by parents 
and teachers. 

248. Important Suggestions in selecting Spectacles. — Whatever be the 
defects of vision which spectacles are designed to remedy, there are 
certain poiuts which should always be observed, both by the maker in 




SUGGESTIONS CONCERNING SPECTACLES. 131 

mounting the glasses, and by the buyer in selecting the frames. It is 

essential that the lenses be so framed that their axes shall be exactly 

parallel, so as to coincide with the axes of vision when the eyes look 

straight forward. Frames are often made so light and flexible aa 

readily to bend in clasping the head, so that the glasses cease to be in 

the same plan, and their axes lose their parallelism. This is shown in 

Fig. 63, where the axes of the len- 

' ,„..,. .^, Fig. 63. 

ses, c a, instead of comcidmg witn , , . 

the axes of vision, a i, are altered in \ / \ i 

their direction, and become conver- 
gent. Again, the most perfect vision 
with spectacles is produced when the 
eye looks through the centre, or in 
the direction of the axis of the 
lens. "Where the eye turns from the 
axial centre of the glass, and looks 
obliquely through it, the view is less 
clear and perfect. For this reason 
persons wearing spectacles general- 
ly turn the head, where those with- The axes of the glasses, c <f, should coin 
*' ' cide ■with the axes of vision, a o. 

out them generally turn the eye. 

The distance between the centres of the lenses should be exactly equal 
to the distance between the centres of the pupils. As the clearest vision 
is through the centres of the glasses, the eyes will have a constant 
tendency to look in that direction. Hence, if the lenses be too far 
apart, the eyes, in striving to accommodate themselves, will acquire a 
tendency to an outsquint ; while if the glasses are too near together, 
there will be, for a similar reason, a tendency to an insquint. The 
frames should not only correctly adjust the glasses, but should main- 
tain them firmly and steadily before the eye. The lenses should bo 
free from veins or small bubbles, be ground to an exact curvature, and 
be perfectly polished and free from flare, or what is technically called 
curdling. "What are called 'pebble-glasses,' or 'pebbles,' are some- 
times used ; they are cut from Brazilian rock-orystal, and have the ad- 
vantage of being more transparent than glass ; they are also much 
harder, do not scratch, take a higher polish, and consequently trans- 
mit more light. 

X.— INJURIOUS ACTION OF ARTIFICIAL LIGHT. 

249. Artificial Light not Wliitc, bnt Colored.— Artificial light diflfers 
from daylight in composition ; it is colored^ while daylight is of a pure 



138 INJURIOUS ACTION OP AKTIFICIAL LIGHT. 

white. "We have seen that white light is a compound, consisting of 
three simple colors, red, yellow, and blue (159). There is no means 
of positively determining the proiiortiou in which these colors combine 
to produce white, although it is commonly stated to be, red 5, yellow 
3, blue 8. Whatever may be the measured quantities in which they 
combine, we know that any disturbance of those quantities destroys 
whiteness and produces a colored light. Now our common artificial 
lights are not really white ; they appear so from want of a pure white 
to contrast with them. They are more or less deficient in blue, and 
consequently appear of the tints which result from a mixture of what 
remain, yellow and red ; these combined produce orange, so that arti- 
ficial luminaries produce in a greater or less degree yellow or orange- 
colored light. 

250. How the fact may be shown. — To become assured of this fact, 
it is only necessary to observe both daylight and candlelight under 
circumstances favorable for comparison, which may be done in the 
following manner. If a lighted candle be placed in a bos, with a 
round hole cut in one side so that the rays may pass through and form 
a luminous circle on a sheet of white paper ; and if then a second 
luminous circle be formed on another part of the paper by a beam of 
daylight admitted through an opening in a closed window-shutter, the 
orange-yellow tint of the candlelight, contrasted with the whiteness 
of the other circle, will then be strikingly apparent. 

251. Order of deviation of different Lights from Whiteness. — The red- 
colored light is produced by the slowest and most imperfect combus- 
tion (188) ; as the burning becomes intenser orange and yellow appear, 
and lastly, at the highest temperatm-e, blue, which by mingling with 
the other colors produces whiteness. The different illuminating sub- 
stances yield lights of various tints, from a dingy red np to white, ac- 
cording to their composition and the various circumstances of combus- 
tion which we have noticed. Dr. J. Hxjntee arranges the lights of 
illuminating substances as degenerating from whiteness nearly in the 
following order. Oil-gas, naphtha ; sperm oil ; coal-gas from the 
best coal ; wax, spermaceti, and stearine candles ; vegetable oils ; 
moulded tallow candles ; coal-gas from inferior coal ; coarse oil and 
dipped tallow candles. Camphene and kei'osene oil will probably 
rank with the best gas, and a good quality of burning fluid with 
spermaceti candles. 

252. Alteration in Colors seen by Artificial Light. — It is well known that 
colors appear dificrently when illuminated artificially than when seen 
Vy daylight. This is a necessary consequence of the difference in the 



ITS EFFECTS UPON THE EYES. 139 

rays which fall upon them. As sunlight contains a large proportion 
of Hue rays, and artificial light an excess of yellow rays, they must 
inevitably influence the color of surfaces in a different manner. In 
artificial light green has a yellow hue, and blue turns green from the 
excess of the yellow rays ; dark blue becomes purple and nearly black ; 
orange, by reflecting its own constitutent rays, appears very bright ; 
yeUow appears white, from there being no really white light to con- 
trast it wnth, and red has a tawny color from the excess of yellow ; at 
the same time all the colors except the orange are much unpaired in 
brilliancy, and many of the deeper shades become quite black and 
sombre, from there not being any pure white light reflected from their 
surfaces, as in daylight, when even the gravest colors have a remark- 
able degree of clearness and purity. Of course the appearance of 
colors by artificial light wiU depend directly upon its quality. The 
whiter and purer and nearer to daylight it is, the more bright and 
natural w411 they be ; while the more colored and dingy the light, the 
more chromatic disturbance and perversion will it produce. 

253. now Artificial Light aflfeets the Eyes. — But the eye itself is 
affected by the use of artificial light, as is shown by the following 
simple experiment, suggested by Dr. James Hunter. " Tie up the 
left eye, and with the other look steadily and closely for about a 
minute at some smaU object placed upon a sheet of white paper, and 
strongly illuminated with ordinary daylight, but not exposed to the 
direct rays of the sun ; then uncover the left eye and look at some 
distant white object or surface, such as the ceiling of the room, first 
with the left eye and then with the right. It will be found that there 
is not much difference in its appearance as seen by one eye or by 
the other, though in general it will be a very little brighter to the left 
eye. After this, darken the room by closing the shutters, tie up the 
left eye again, and then with the right one look at the same object 
placed on a sheet of white paper as formerly, but illuminated by a 
large tallow candle or oil lamp, so that it shall be seen as distinctly as 
It was in daylight. Keep the right eye fixed on this object for about 
a minute, so as to examine it closely and narrowly, tlien extinguish 
tlie candle or lamp, open the shutters, and uncover the left eye. 
"When both eyes are now turned to the ceiling, it will appear some- 
what dim and indistinct ; and on looking at it first Avith the one eye, 
and then with the other, the difference will be very remarkable. To 
the left eye, which had not been exposed to tlie action of the artificial 
light, it wiU appear unchanged, or soinetimes of a pale yellownsh- 
^'hite color ; but to the right eye it will be very dim and of a darh 



140 INJURIOUS ACnON OF ARTIFICIAI, LIGHT. 

Hue or purple color. The effect produced npou the right eye in this 
experiment soon goes off; and though it always takes place to a cer- 
tain extent when artificial light is used, it is not much ohserved, 
because as both eyes are equally affected, the contrast is not very 
striking. But if any one will read or write by candlelight for some 
hours with one eye closed, he will be rendered fully sensible of its 
very injurious action, when he afterwards compares the state of one 
eye with that of the other, 

254. Explanatiou of these effects. — "We shall understand these effects 
by recalling what has been said of complementary colors (173). "When 
the nerve of vision is exposed to a colored light, it is unequally excited. 
The equilibrium of its action seems to be disturbed. It becomes less 
sensitive to the observed color, and when the eye is afterwards turned 
to white objects, they do not appear white but tinged with the com- 
plementary to the one seen first. The continued action of one color 
seems to paralyze the retina to its influence, and produce an unnatural 
sensibility to the other colors, which, combined with that, compose 
white light. In the preceding experiment, the eye, stimulated by 
candlelight, in which orange-yellow is in excess, temporarily lost its 
power of discerning white, and saw in it only the complementary of 
orange-yellow, blue or dark violet. 

255. How this may injure the Retina. — Now the effect of this over- 
stimulating the nerves of vision through excess of red and yellow 
rays, on the part of those who use their eyes much by artificial light, 
is often to produce at certain points of the retina a total insensibility 
to those rays. The consequence of this is, that in daylight dark films 
of a blue or purple color, which are complementary to the orange or 
yellow color of the artificial light, appear before the eyes. The pecu- 
liar color of these films is not very obvious, unless they are seen in 
contrast with a yellow or orange surface, and over them they appear 
very sombre and almost black ; because, in the peculiar state of the 
eye that gives rise to their appearance, there always coexists a certain 
degree of diminished sensibility to all the rays composing white 
light. 

256. Popular recognition, of the effect of different Colors. — There is a 
difference in the effect of different colors upon the eye. which is 
generally recognized and variously expressed. Thus blue is said to be 
a very soft, cool, retiring color ; green is cool, though less so than 
blue ; yellow is warmer and advancing ; orange still warmer, and red, 
Jiery, harsh, and exciting. This agrees with the view which regards 
blue and green as least hurtful, and yellow, orange and red as more 



i 



ITS ASSOCIATED HEAT. 141 

irritating and injurious to tlie eyes. An explanation of tlaese different 
effects is found in the wave theory of light and colors, which has 
been previously noticed (155). Vibrations of the red ray are larger 
and more forcible than those of the yellow, and the yellow than those 
of the blue, just as the large and slow heavings of a swell upon the 
ocean are more violent and irresistible than the smaller and quicker 
ripple-waves. 

257. Heat aceompaaying Colors — The above current phrases in refer- 
ence to the coolness and warmth of color, correspond perfectly with 
the distribution of measured heat among the several colors of the 
spectrum. We all know that heat is associated with light ; but it is 
not equally associated with each color that composes the light. 
When the colors of the sunbeam are separated and spread out as in 
the spectrum, it is found that the heat is least intense at the blue, and 
constantly increases through the green, yellow, orange, and is most 
intense in the red color. Thus Englefield found that while the blue 
rays were at a temperature of 56°, the yellow were at 62°, and the 
red at Y2°. Thus the orange and red of common artificial light are 
actually more fiery and exciting than the absent blue rays. This ac 
companying heat is apt to be much more inj urious in artificial than in 
natural light. The sun's rays are seldom, if ever, allowed to fall 
directly on a near object on which the eyes are to be employed for 
any length of time, without having previously undergone repeated 
reflections from the atmosphere and clouds, or from the sux-face of the 
ground and walls and furniture of the apartment, which absorb a 
great portion of their accompanying heat. But owing to the non- 
diftused and concentrated character of artificial light, the rays must 
be generally allowed to fall directly on the object looked at, from 
which they are reflected to the eye along with nearly the whole of 
their accompanying heat. 

258. The Lnminons Matter being imperfect, more mnst be used. — The 
luminous effect, or as it is termed the defining power of light, that 
quality by which we are enabled to see minute objects with the most 
distinctness and ease, is much less in artificial light than in the white 
light of day. This lower defining power of orange-colored light 
makes it necessary to increase the amount of the inferior rays ; we 
attempt to compensate for deficient quality by excess in quantity. In 
reading by daylight the black ink is strongly contrasted wilh the pure 
white paper ; but by artificial light, as the paper has an orange or yel- 
low hue, the contrast is not so marked, and so to aid vision, the quantity 
of light is increased. In severe, long^continued, and nightly exercise, 



142 INJURIOUS ACTION OF ARTIFICIAL LIGHT. 

as in reading, writing, sewing, type-setting, &c., the injurious conse- 
quences of impure light are apt to be heightened by its excessive use. 

259. Carbonic Acid alTects the Eyes. — Sunlight does not poison the 
air, artificial light does. In proportion to its brilliancy and abundance, 
the insidious narcotic agent, carbonic acid gas, is generated and set 
free. The effects of breathing this substance will be described when 
treating of the air and ventilation (293) ; but it may be remarked, that 
by its special influence in deranging and disordering the nerves, it is 
fitted to concur with those influences which impair the action of the 
retina. 

260. Unsteadiness of Artificial Light injarions. — Sunlight never wavers 
or flickers ; its action upon the eye is equable and unvarying. But in 
artificial illumination, as it is impossible perfectly to regulate the sup- 
ply of air and of combustible material, the light is flickering and un- 
steady. The glass chimney of the Argand burner, however, produces 
the most constant and unchanging flame. The bad effects of these 
sudden and continual alterations in the brightness of artificial light, 
may be shown by supposing that a minute object can be seen in light 
of 8, 9 or 10 degrees of intensity, but that the intermediate degree of 9 
is best .Now if sunlight be used, as it flows in a perfectly uniform man- 
ner without sudden variations, the retina and pupil adapt themselves 
to its quantity, and the eye may be long used without fatigue. But if 
artificial light of 9 degrees be used, it may at one moment rise to 10, 
and at the next fall to 8 degrees, from the fiickering of the flame, so 
that the retina and pupil have not time to accommodate themselves to 
the change, and a degree of temporary blindness or impaired distinct- 
ness of vision, results, which is very straining and fatiguing to the 
eye. To remedy this, the light is increased in intensity. If it b<3> 
raised, say to 14 degrees, then it may be reduced to 13 or rise to 15 
degrees, without immediate inconvenience to the eye ; there being 
abundance of light, its variations are less sensible. This relief, how- 
ever, is fraught with ultimate danger ; for the retina is too much 
excited by this increase of one-half in the quantity of light admitted 
to it ; and this state of excitement is but the prelude to an opposite 
state, in which the sensibility to light is greatly, and perhaps perma- 
nently diminished (265). Unsteadiness of the object viewed, if the 
eye be long and closely directed to it, is a source of injury. It is thus 
that much reading in railroad cars, whore the trembling or incessant 
movement of the i)rint keeps the image in constant motion upon the 
retina, has a bad influence upon the eye. 

261. All Light iiynrions bnt that from the objects Tlewed. — The distinct- 



THE EYE BLINDED BY EXTRANEOUS KAYS. 143 

nesg of vision is interfered with, and the eyes made to suffer by an- 
other important circumstance— tlie admission of light into the eye 
from other sources than objects to which sight is directed ; in other 
words, the introduction of extraneous light into the eye. Impres- 
sions upon the retina may be diminished and obliterated by other 
rays falling upon it, which excite the nerve more strongly. The moon 
at night, as we all know, produces a vivid impression upon the nerve 
of visual sense. It produces precisely the same impression in the 
daytime, but then the luminous image is extinguished by the over- 
powering light of the sun, so that we are not conscious of it. Wlien 
we are using the eyes upon any object, all light which enters them, 
except from tJiat olject, is injurious ; that is, it has a blinding effect. 
This is shown by the greater clearness of objects seen through a tube, 
where all the diffused and side-light is excluded, on the same principle 
that persons see stars from the bottom of a well in the daytime.* Or it 
may be shown in another way. Let a person stand before a gas-light 
in such a position, that in reading a book a considei'able number of 
the direct rays from the flame shall enter the eye. Let him then 
cautiously reduce the light by turning the stop-cock until the letters 
can be no longer distinguished. If he now shade bis eye by inter- 
posing his hand or a screen, so as to cut off the direct rays, the words 
will again become visible, and again disappear when the hand or 
screen is removed. This proves that when the eye is protected from 
the direct rays, small objects can be seen with less light, and conse- 
quently with less injury to the nerve of vision. 

262. Prevalence of this source of injury. — Upon this point Dr. Hun- 
ter remai-ks : " Though the injurious action of artificial light, in con- 
sequence of its improper position, can be easily obviated ; it is aston- 
ishing how little it is attended to, and how generally it is in operation. 
For the express purpose of satisfying myself on this point, I have 
visited a great many workshops, printing-houses, tailors' rooms, and 
other places, and in almost every instance I found the artificial lights 
placed close to, and directly opposite the eyes of those engaged in fine 
work, requiring the excessive exertion of the sight, and frequently the 
mischief was increased by concave metallic reflectors, placed behind 
instead of around the light. Now that gaslight is so generally em- 
ployed, its improper position is a most serious evil ; for as its intensity 
can be so easily increased in proportion as the sensibility of the eye 
becomes impaired, few persons, particularly those who are igno- 
rant of the harm they are doing, can resist the temptation to use a 
• Humboldt, however, questions if stars are ever thus seen. 



144 INJUBIOUS ACTION OF ARTIFICIAL LIGHT. 

stronger and stronger liglit, till at last their sight is permanently 
weakened or even quite destroyed." 

2G3. Bad Light may inflame the Eyes. — The continued action of im- 
proper light upon the eye is liable to inflame it. The first symptom 
is a reddening of the lining membrane of the eyelids, which in health 
is of a white or pale rose-color. This may be observed by gently 
drawing down the lower lid, when its surface will be seen injected 
with blood and of a deep red color. At first there may be but little 
uneasiness in the daytime, but at night, when the eyes are employed 
on objects illuminated by a candle, they become hot, watery, and 
irritable, the lids feeling dry, stiflT, and itchy, and causing the patient 
constantly to rub them. The dryness, after a time, may give place to 
a copious flow of burning tears, which suff"use the eyes, and pour over 
and scald the cheek. Sometimes there is an excess of gummy and 
adhesive secretions, which dry at night and glue together the lids so 
hard as to require long bathing with warm water before they can be 
opened. If this incipient inflammation be unchecked, it may increase 
and run on to various forms of disorganization, or it may take the 
shape of a chronic or unmanageable affection of the eyes without pro- 
ducing blindness. 

264. Unnatural increase in the sensibility of the Retina* — In the preced- 
ing case, the disease is located in the external or image-forming por- 
tions of the eye, but the bad management of artificial light is apt to 
engender a far more dangerous and intractable form of disease, which 
fixes itself upon the image-feeling parts — the retina and optic nerve. 
The excessive use of impure light, by its unequal action, excites and 
stimulates the nerves of vision, producing an unusual irritability to 
light, and a low degree of inflammation of the retina. Moderate light 
becomes unpleasant, and the individual, after looking steadily at some 
object for a few minutes and then closing the eyes, or putting out the 
light, appears to see still before him quite a distinct representation or 
image of the object, which may last for two or three minutes, and be 
variously colored or pass through a succession of colors. It moves, 
but its motions are in opposite directions to those of his eye, for it 
passes upwards when he looks downwards, and sinks downwards when 
he rolls his eyeballs upwards. It is caused by the morbidly increased 
sensibility of the retina, which retains the impressions of light for a 
greater length of time than when it is in a healthy condition. This 
state of the eye is accompanied often during the daytime by a dull, 
heavy feeling in the forehead, hardly amounting to pain, but causing 
the patient frequently to pass his hand across his brow, and in read- 



ITS MOKBID EFFECTS UPON THE KETINA. 145 

ing or writing at night, there is an unpleasant sense of distension in 
the orbits, with an increased flow of tears and frequent twittering or 
quivering of the eyelids. Brilliant flashes of fire are seen, particu- 
larly when the eye is touched, on lying down, and after reading, writ- 
ing, or sewing for some time by artificial light. 

265. Decrease in nervous sensibility— Appearance of dark films. — This 
condition of excessive irritability may continue for months, and then 
be followed by others totally different, and indicating a diminished 
sensibility of the nerves of vision. This is evinced by the appearance 
of dark spots or films floating in the air. At first but one film appears 
before each eye, which is seen only for a moment, and then darts away, 
shortly to reappear. But afterward their number is increased, tliey 
appear oftener, are larger, darker, more opaque, and continue longer 
visible than at first. They sometimes look like cobwebs, or flakes of 
soot, or bunches of fur-down. They often resemble large-sized leaden 
shot, or minute and transparent globules, looking like drops of oil upon 
the surface of water, and, connected with each other like tlie links of 
a chain, float slowly through the air. These appearances are known 
by the doctors as muscm volitantes; they are probably connected with 
morbid conditions of the nerves, but how we do not know. 

26G. Paralysis of the nerve of vision — Amanrosis. — These appearances, 
in their less marked form, are quite common, many eyes being subject 
to them, and they may occur for a long time without getting worse, 
and unaccompanied by positive disease. But when they appear as a 
dense, opaque, stationary film, which interrupts and obscures vision, 
the symptoms become very alarming ; there is danger of palsy of the 
retina producing nervous blindness, or amaurosis. To the casual ob- 
server, the eye, under the influence of this malady, appears perfectly 
well, there being no external evidence of disease. But when once 
seated, its effects may be seen in the irregular shape of the pupil, 
which loses its roundness while the motions of the iris under the in- 
fluence of varying light, become sluggish and imperfect, or are alto- 
gether lost. Objects appear clouded in a thick mist, and the air some- 
times seems filled with sparkling, glittering points. In the final 
stages of amaurosis the pupil is very much dilated, the sight is impaired 
or quite gone, and the eye has a lustreless, dead appearance. As the 
disease advances pain ceases, the light, instead of being disagreeable, 
as at first, can hardly be procured of sufficient intensity. The patient 
I'esorts to spectacles of a high magnifying power, whicli condense a 
great quantity of light upon the palsied nerve of vision ; these may 
afford transient aid, but do ultimate injury. This disease may require 
1 



146 manage:ment of artificial light. 

from a few months to several years to run its course, but araaurotio 
blindness is regarded as incurable. 

267. Who are most subject to amaarotic disease. — Amaurosis may arise 
from other causes than the improper use of artificial light, but Dr, 
Elliott states that nearly two-thirds of all the cases of this disease 
which are met with in practice, occur in those who use their eyes 
much by artificial light, such as literary men, students, compositors, 
tailors, seamstresses, shoemakers, engravers, stokers, glass-blowers, 
&c. He also remarks that some individuals are more liable than others 
to suffer from the injurious action of artificial light, particularly those 
of a fair complexion and with gray or light blue eyes. 

XI.— MANAGEMENT OF AKTIEICIAL LIGHT. 

268. Effect of gronud glass Shades.— We have stated (261) that all 
light which is more intense than that coming from the object viewed, 
dazzles the eye and weakens the impression of the object, causing it 
to appear less clear and distinct. To cut off theSe blinding rays from 
the flame itself, translucent screens of ground glass, caWed shades, globe- 
shaped, or of any other desirable figure, are made to surround the lu- 
minary, and have the effect of deadening the light in a surprising man- 
ner. The outline of the fiame disappears, while the rays of fight come 
from the surface of the globe, which thus appears self-luminous, and 
emits a diffused and softened light. As the rays cross each other at 
aU points, and are scattered in all directions, objects near by throw 
only short, indistinct shadows, and there is a general and equal illumi- 
nation. These shades should be used whenever it is desired to reveal 
to the best advantage the objects of a room, but where the vision is to 
be specially exerted upon particular things, then* use is unfavorable, 
as by diff'usion there is considerable loss of light. Objection has been 
made to the employment of ground glass and semi-transparent white 
ware shades, on the ground that by scattering the light they expand 
the impression over a larger surface of the retina ; but as the image en- 
larges in area, it diminishes in intensity, which is desirable, unless the 
eye is constantly engaged in the scrutiny of minute objects. 

269. How to collect the Light — Reflectors. — It is apparent that the ra- 
diation of light in all directions, is favorable to the equal illumination of 
objects distributed in all parts of the room. But when we desire to 
view closely minute objects, as in reading, writing, sewing, &c., it is 
necessary to concentrate upon the point of observation the light which 
would be otherwise wasted by general diffusion. To collect the rays. 



EMPLOYMENT OF SUADE8. 



147 



and direct them to the part where they are required, conical shades or 
reflectors, of tin, paper, or some other opaque substance, and usually 
polished or whitened on the inside, are made to surround the flame. 
These not only protect the eyes from the glaring rays, hut direct down- 
wards that which would escape iu other directions and be lost. 

270. Bine Shades to supply the missing rays. — To remedy the defects 
which arise from the bad composition of artificial light, several expe- 
dients have been suggested. It is proposed to surround the flame with 
a conical shade, the inner side of which is sky-blue. As the light that 
passes upward, falls upon this surface, its red and yellow colors are 
absorbed, and the few blue rays which it contained, being thrown 
downward by the sloping sides of the reflector, mingle with the 
orange light, proceeding directly from the flame, and improve the bad 
color by imparting to it a higher degree of whiteness. As in this 
case a portion of the reddish yellow rays are absorbed, there is a loss 
of light. If a common white reflector is used, more luminous matter 
is thrown down than with the blue shade, and a stronger illumination 
is produced. But, with a blue reflector, although there is less bril- 
liancy, the light is whiter, purer, and has a higher defining power, 
while it is cooler, more agreeable, and less injurious to the eyes.* 

271. Strnctnre and monnting of these Shades. — Shades of bristol-board, 
or strong paper, or silk, may be made by 
any one. The material is to be cut into 
the shape exhibited in Fig. 64, and then 
the edges, a a and & 5, are to be united 
to each other, which gives rise to the 
conical structure shown in Fig. 65. This 
may be mounted upon a wire frame, 
which is to be hooked on to the glass 
chimney,or ground shade, or in the ab- 
sence of these, a wire framework may be supported by the body of 
the lamp. If the reflector be made of metal, as tin or copper, it may 
be sustained either in the way described or by a three-branched sup- 
port, screwed on to the burner. Eeflectors are 
adapted to candles by attaching to the candlestick 
an upright brass rod, on which the reflector slides, 
being fixed at any point by a thumb-screw. This 
is shown in Fig. 66. 

272. Dow bine Reflectors should be colored. — The 
most pure and unchangeable blue color is ultramarine, and this is best 



Fig. 64. 




Fig. 65. 




♦E. V. HAroHwouT, of 490 Broadway, N. Y., fuinisLes those shades. 



148 



MANAGEMENT OF ARTIFICIAL LIGHT. 



Fig. 




Candlestick with 
shade. 



adapted for paiuting the inner surface of shades, Prussian-hlne de-' 
composes and turns green by exposure to the heat, and other coloring 
matters are liable to fade or change. The colored 
surface should be smooth, but without gloss or var- 
nish, the surface appearing dead, or, as it is techni- 
cally termed, ' flat.' 

273. Artificial Light whitened by absorption. — Blue, 
transparent media absorb the yellow and red rays, 
and transmit only those of blue. If the glass chim- 
ney of a lamp be tinted lightly and evenly with a 
mixture of ultramarine and mastic varnish, the of- 
fensive orange will be separated from the light as it 
passes through, but at the expense of its brilliancy ; 
there will be much less of luminous matter. But if 
a polished tin or silvered reflector be emploj-ed to 
collect the rays, it will throw downward a beautiful 
soft white light. If the light from a luminary which 
is surmounted by a white or polished reflector (Fig. 
67) be made to pass through a glass globe filled with 
water which has been slightly blued, its color wiU be 
improved, whUe to compensate for the loss of luminous matter ab- 
Fig. 6T. sorbed, the spherical form of 

the water-bottle will serve to 
converge or gather the rays so 
as greatly to increase their illu- 
minating power, at tlie point 
upon which they fall. Mello- 
Ni has proved that when the 
rays of artificial light are passed 
through even a very thin stra- 
tum of water, their heating 
power is diminished by eighty- 
nine per cent., but with little 
increase in the temperature of 
the water, in consequence of its 
great capacity for heat (49). 
The water-globe thus transmits 
a cooler as well as a whiter and 
purer light. Lamp-globes made 
of f;lass, sliglitly blued in its composition, would be very desirable. 
274. ColM-cd glasses for Spectacles. — The indiscriminate use of these 




AVhltcnlng the rays and straining them of 
their heat. 



COLORED GLASSES — MISUSE OF GAS. 149 

is altogether objectionable. They place the eyes iu very unnatural 
conditions as regards the light, and if their employment is persisted in, 
it impairs their sensibility to the true relations of color, and otherwise 
injures them, as we have just seen that artificial colored light is able 
to do (253). If we look through a glass of any color, the effect is, that 
when it is withdrawn, the eye sees all objects tinged by its comple- 
mentary. As the colored glass cuts off a largo quantity of light, its 
removal produces a sudden and injurious impression. Faint blue 
glasses may be serviceable in using artificial hght. Colored glasses 
absorb and accumulate the heat so as in many cases to be disagreea- 
ble. Their bad effects are more marked, as it is for ' weak' eyes that 
they are generally commended. They may, at times, be of sei'vice to 
protect the eye from an intense glare, as of snow or the surface of 
water in sunsliine. Gray glasses, or what is called a ' neutral tint, ' 
that is no particular color, are perhaps best ; they should not be of too 
dark a shade. 

275. Is Gas-liglit injurious ? — There is a prejudice against gas-light, 
as being the most injurious form of artificial illumination. As against 
the proper and well-regulated use of gas, this prejudice is entirely 
groundless, but there can be little doubt that from its abuse and bad 
management it is really doing more mischief than any other kind of 
light ; its very excellencies are turned to bad account ; its extreme 
cheapness, compared with other sources of illumination, naturally leads 
to its use in excessive quantities ; floods of light are poured forth, so 
that persons may read and sew for hours together in the remotest cor- 
ners of the room. The air is heated by the excessive combustion, and 
poisoned by large quantities of carbonic acid, which there are no means 
of removing. The eye is unprotected from the glare by screen or shade ; 
extraneous light is freely admitted, which obscures the impression and 
strains the nerve of vision, and in proportion as the' sensibility of the 
eye is impaired, stronger light is used, which gives temporary relief, 
but with danger of ultimate and permanent injury to the sight. On 
the other hand, good, well purified gas, judiciously controlled in ac- 
cordance with the hints we have given, and others to be offered in the 
next part, is perfectly harmless (360). 



PART TIIIllD. 

AIE. 



I.— PROPERTIES AND COMPOSITION OF THE ATMOSPHERE. ' 

276. Part it plays in tlic scUenie of Nature— It is impossible to con- 
template the wonderful properties of the atmosphere Avithout a feeling 
of profound amazement. "Whether we regard it as the grand medium 
of water circulation, through which rivers of vapor lifted from the 
oceans are carried landward, to be condensed and channel their way 
back again to the sea ; or as the scene of tumultuous storms, generating 
the lightnings within its bosom, and taking voice in the reverberating 
thunders ; whether as hanging the landscape with gorgeous cloud- 
pictures, or as the vehicle through which all melody and beauty and 
fragrance are conveyed to the portals of sense — it is alike strange and 
interesting. But when we glance at its deeper mysteries, those inti- 
mate relations to life which have been disclosed to modern science ; 
when we consider that the vegetable kingdom not only Las the same 
chemical composition as the air, but in its mass is actually derived 
from it ; that the whole architecture and physiology of trees, shrubs, 
and plants, are conformed to atmospheric nutrition, so that in literal 
truth the forests are but embodied and solidified air, the subject rises 
to a still higher interest. And more startling yet is the surprise when 
we recollect not only that the materials of our own bodily structures, 
derived from vegetation, have the same atmospheric origin ; but that 
active life, the vital union of body and spirit, and all the powers and 
susceptibilities of our earthly being are only maintained by the action 
of air in our systems ; — air which we inhale incessantly, day and night, 
from birth to death. There is an awful life-import in these never- 
ceasing rhythmic movements of inspiration and expiration, this tidal 
flux and reflux of the gaseous ocean through animal mechanisms. 
Sliall we question that it is for an exalted purpose ? Science has many 



IT CONSISTS OF PONDKKABLE MATTElt. 151 

things to say of the relations of air to life, but it can add nothing to 
the simple grandeur of the primeval statement, that the Creator 
"breathed into his nostrils the breath of life, and man became a 
living soul." 

277. Air a material reality — Its pressure. — The atmosphere is so thin 
and invisible, and so totally unlike the objects that present themselves 
to our most impressible senses, that we are half inclined to forget that 
it is a reality, and are too apt to think of it as being mere empty space. 
Yet it consists of ponderable matter, and is heavy, just like the solid 
resisting objects which we see and handle, and it presses down upon 
the ground with a force proportional to its weight. Upon every 
square inch of the earth's surface there rests about 15 lbs. of ail'. 
Upon the body of a medium-sized man, having a surface of 2,000 
square inches, the atmosphere exerts an external crushing force of 
30,000 lbs. But there is air also within the system which exerts an 
equal outward pressure, and thus prevents injury. The pressure of 
air upon the body is not the same at all times. There are tides in it, 
just as there are in the ocean, great atmosi^heric waves which regu- 
larly sweep over the earth and cause the weight of the atmosphere to 
vary. Winds and storms produce similar eifects. These variations in 
atmospheric pressure are measured by the barometer (60), and they 
are so considerable that a man's body may sometimes have from one 
to two thousand pounds more pressure upon it than at others. Of 
course, as the pressui'e upon the air increases from above, more of it 
is crowded into the same space, and it becomes more dense. The 
maximum height of the barometric column, therefore, corresponds to 
the greatest density of the air, and a low condition of the mercury to 
rarity of the air. 

278. Weight of varions masses of Air. — As the air is thus ponderable, 
it is desirable to obtain definite ideas of the proportion between its 
bulk and weight. A cubic foot of air weighs 538-1 grains, or some- 
thing more than an ounce. 13-06 cubic feet weigh 1 lb. About 65 
cubic feet of air furnish 1 lb. of oxygen. An apartment 8 feet high, 
12 wide, and 13 long, contains about 100 lbs. of air ; and a room 40 
feet square and 18 feet high contains about a ton. The atmosphere is 
estimated to be 45 or 50 miles high, but the great mass of it lies close 
to the earth, as it grows very rapidly thinner and rarer in ascending 
from the earth's surface. Indeed if it were all the way up of tho 
same density as that which we breathe, it would be only about fivo 
miles deei^, just sufficient to cover the highest mountains. 

279. Effects of varying pressure of the Air. — Every variation of at- 



152 PKOPEBTTES AND COMPOSITION OF TIIE ATMOSPHEEE. 

mosplieric pressure must decidedly influence the state of the body, 
modifying, as it were, the tension of the whole fabric, affecting the 
pores of the skin, the cells of the lungs, and the circulations within 
the system. The constitutions of many invalids, especially the asth- 
matic and consumptive, are undoubtedly much influenced by changes 
of atmospheric density. As the barometer falls and the air becomes 
lighter, the tendency to evaporation from all surfaces, and the amount 
of expansion in all the more compressible tissues increases. As the 
lungs have a constant capacity, and consequently receive the same 
bulk of air at all times, it is clear that the quantity taken into these 
organs to act upon the blood will vary with its density, there being of 
course more matter in a chest-full of dense air than in a chest-full of 
light air. Such changes, which powerfully influence the general rate 
of action within the system, must affect the mind as well as the body, 
and assist to explain the fact that "persons are often joyful, sullen, 
sprightly, hopeful and despairing, according to the weather, while 
there are days in which the faculties of memory, imagination and 
judgment, are more acute and vigorous than others." Every alter- 
ation of an inch in the mercury of the barometer adds or removes a 
weight of 1,080 lbs. from the average weight which a man of common 
stature sustains. The effects of sudden alterations of this pressure, as 
when the barometer is subject to rapid and extreme variations, often 
appear in the shape of headache and apoplexy (779). Yet in this, as 
in numerous other cases, it is remarkable to what different states the 
system can habituate itself. Sausstjre, at the summit of Mont Blanc, 
had scarcely suflicient strength to consult his instruments ; while at 
heights scarcely inferior, South American girls will dance all night. 
The influence of fluctuating pressure of the air is of great importance 
to the inhabitants of low, swampy, malarious districts of country'. 
The amount of exhalation and effluvia which rise from the ground 
depends much upon atmospheric pressure. When the air is heavy, 
these substances are, as it were, confined to their sources, that is, they 
are liberated at the slowest rate ; but as the barometer falls the pres- 
sure is taken off, and the miasmatic emanations rise much more 
freely (301). 

280. Of what the Air is composed. — Now we can study all about at- 
mospheric pressure, and many other things concerning the air, without 
ever asking what it is made of; but before we can kaow why it 
is that animals breathe, Ave must understand its chemical properties. 
We have referred to the constituents of air in connection with the 
subject of combustion (74) ; we are now to examine it* composition 



RELATIVE PKOrOKTlON OF ITS CONSTITUENTS. 



153 



and endowments more fully in relation to life. The atmosphere con- 
sists of four substances, — a pair of elements, nitrogen and oxygen, 
and a pair of compounds, carbonic acid gas and vapor of water. Dry 
air contains by weight very nearly 77 per cent, of nitrogen to 23 of 
oxygen. The proportion of moisture in the atmosphere varies with 
the temperature ; when saturated at 60°, it contains about 1 per cent., 
and it has an average of about l-2000th of carbonic acid. These pro- 
portions are thrown into visible form by the diagram (Kg. 08). In 
addition to these definite and stable elements, of which the atmosphere 
is universally composed, various gaseous exhalations from the earth 



Nitrogen, or the diluting constituent 
of the Air. 



Oxygen, or the active constituent of 
the Air. 



Moisture, or the variable constituent 
of the Air. 



Carbonic Acid, or the poisonous con- 
stituent of the Air. 



The areas of blackened surfoeo represent tlic rela- 
tive proportions by weight of the constituents of 
the Air. 

constantly enter it, though so minutely as generally to elude detection 
and identification. LiEBia has shown that a trace of ammonia is 
always present in it (299). 

281. Intermixture, or diffnsion of Gases. — These gases have different 
weights. The oxygen is slightly heavier than the nitrogen ; the watery 
vapor is much lighter than either, and the carbonic acid about half as 
heavy again as the air itself. It might seem, then, that if they were 
mingled together they would gradually separate and arrange thera- 
Belves in distinct layers, the heaviest at the bottom and the lighter 
above. Some works on ventilation have actually stated such to be 
the case, and that when we breathe out vapor of water and carbonic 
acid, the former rises while the latter descends. One of them re- 
marks : " were these different portions of air as tliey come from the 
7* 




164 EFFECTS OF THE CONSTITUENTS OF AIR. 

lungs, of different colors, we should, in a perfectly still atmospherei, 
Bee the stream divided, part of it falling and part ascending." This, 
of course, is not true. If such were the fact, if gases tended to 
arrange themselves in the order of their gi'avities, and there were no 
universal and inflexible law to prevent it, the carbonic acid of the air 
might slowly sink to the earth, and form a deadly stratum 10 or 15 
feet deep over its entire surface, or fill up all its valleys with treacherous 
invisible lakes of aerial poison. But such is not the tendency of 
things. Gases brought together, no matter what their different 
weights or varying proportions, diffuse throughout each other so as 
to become perfectly and equally commingled. Heavy gases will rise 
up to mix with lighter ones, and lighter gases descend to mingle with 
those that are heavier. As a consequence of this important law, the 
proportions of the atmospheric gases to each other are kept extremely 
uniform, being scarcely, if at all, influenced by season, climate, wind, 
Aveather, or even the salubrity of the air. How benign and admirable 
is this provision of nature, by which, without being aware of it, we 
are relieved at every instant of a deadly though invisible poison, the 
process continuing as well during sleep as while awake, and taking 
place as perfectly for the unconscious babe as for the matured man. 
This great law secures the unity of the atmosphere. Its ingredients 
are perfectly mingled and equally diffused throughout each other, but 
not chemically combined^ so that in breathing, although we separate 
the constituents of the air, we do not have to chemically decompose 
it. When we speak of air we mean the mass of commingled gases 
acting together ; yet as each constituent preserves its identity, and 
produces its peculiar' effects, it is necessary to consider them 
separately. 

II.— EFFECTS OF THE CONSTITUENTS OF AIR. 

1. NiTEOGEX. 

282. This gas seems to take no active part in breathing; it 
passes out of the body as it entered it, without being changed, A 
fire cannot be kmdled in it, and an animal breathing it quickly dies, 
though not from any positive noxious effect which it produces, but 
rather from want of something else. Nitrogen is a negative or inert 
Bubstance, its chief use being to dilute or temper the other active in- 
gredients of the air to a proper degree of strength. 

2. OxTGEisr. 

283. How the System is charged with Oxygen. — Of the wonderful in- 



OXYGEN — HOW IT ENTEES THE SYSTEM. 



155 



Fig. 69. 



fluence of this agent we can here speak but briefly, as the subject will 
have to be considered again more fully in treating of the action of 
foods. We have noticed that oxygen is the active agent in combus- 
tion, so it is also in breathing. It is on account of what it does in our 
system that we respire the atmosphere. The air enters the lungs 
thrSngh the windpipe and bronchial tubes or air passages, as seen in 
Fig. 69. It fills and distends the numberless little cavities or air-cells^ 
which are enclosed by these membranes, and overspread with the finest 
network of capillary blood-vessels. Oxygen then penetrates or passes 
through the delicate membrane and enters the blood, imparting to 
it a bright crimson color, and rushing forward with it through what 
is called the pulmonary vein (Tig. 70) to the heart. It is estimated that 
the lungs contain, on an average, 220 cubic inches of air, with an 
inner membrane surface of 440 
square feet, nearly thirty times 
greater than the whole exterior of 
tlie body.* This vast extension of 
surface is to secure the largest and 
most perfect opportunity of action 
and reaction between the air and 
blood. From the heart the blood 
passes by the arteries to aU portions 
of the body. These arteries divide 
and subdivide until they are reduced 
in size to the finest hairlike tubes, 
which are densely interlaced through- 
out all the tissues of the body. 
The arterial channels thus represent 
streams of oxygen flowing from the 
lung fountains to every portion of 
the system. In this way each mi- 
nute part of the living fabric is in 
direct communication with the ex- 
ternal air, that it may receive from 
it the agent upon which it imme- 
diately depends for the performance 
of its vital offices. This system of 
ai-terial currents, bearing oxygen /row the air to every portion of the 
system, implies a set of counter-currents to drain olf the poisons gen- 
erated witbin the body, back into the air. This is the duty of the veins 
or venous system. In the accompanying diagram (Fig. 70), the fiuo 

* Dr. Addison estimates the number of air-cells iu the two lun^s at 1,7W,000,000, 
*ml tiic extent of the membrane at l.OOO square feet. 




rl 

Human Lung. 
a the larynx; h windpipe \ ec c bron- 
chial tubes or air passages ; e lung. 



156 



EFFECTS OF THE COKSTmJENTS OF AIE. 



vessels at the top represent the lungs, and those at the bottom the 
capillaries of the whole body. The double circulation is shown, and 
how the heart is related to it. The A'essels on the right side represent 
the arteries carrying blood charged with oxygen, and those on tli* left 
side, tlie veins, conveying carbonic acid. 

Fig. to. 
Lesser or Pulmonary Circulation. 



Pulmonary 
Artery. 



Eight Ventricle. 




Pulmonary 
Yein. 



Left Auricle. 



Vena Cava. .. 



Loft "Ventricle. 



Aorta. 



Greater or Systemic Circulation. 

284, What Oxygeu does in the body. — The purpose of this incessant 
inflowing stream of oxygen, is to carry forward the great operations 
of the vital economy. Oxygen has a wide range of chemical attrac- 
tions, and combines with other elements with intense energy. It is 
the ever-laboring^ tireless Hercules of the atmosphere. As it kin- 
dles and maintains the combustion of our fires, so it does our bodily 
vitality. The muscles are called into action through decomposition 
by oxygen, and as with the muscles in the manifestation of mechani- 
cal force, 80 with the brain in the exercise of intellectual power. This 



INFLUENCE OF OXYGEN — MOISTURE. 16 7 

organ is on an average only about g'^ the weight of the whole body, 
yet it receives from ^th to ygth of the entire oxygenated stream from 
the lungs and heart. A torrent of oxygen is thus poured incessantly 
into the material apparatus of thought to carry forward certain physio- 
logical changes upon which thinking depends. If the arterial stream 
be cut off from a muscle, it is paralyzed ; if it be stopped from the brain, 
unconsciousness occurs instantaneously. In proportion to the activity 
of muscle is its demand for the destructive agent ; in proportion also 
to the activity of the mind is the brainward flow of arterial blood. 

285. Eflfccts of rarying the quantity of respired Oxygen. — If an animal 
be deprived of this gas, it dies at once. If man undertake to breathe 
a less proportion than that naturally contained in the air, the effect is 

depression of all the powers of the constitution, physical and mental, 
to an extent corresponding with the deficiency. If the nutural amount 
be increased, there is augmented activity of aU the bodily functions, 
the life-forces are exalted, and the vital operations are driven at a 
preternatural speed. If pure oxygen is respired, the over action and 
fever become so great that life ceases in a short time. Nitrous oxide 
(laugMng gas) is a compound rich in oxygen, and when presented to 
the blood it absorbs a much larger proportion of it than of pure oxygen. 
Hence, when this gas is breathed, the blood drinks it up rapidly, and 
the system becomes so saturated with it as to produce the most remark- 
able effects. The muscular energy is so aroused that the inhaler is 
often impelled to extraordinary feats of exertion, and the inteUectual 
powers are excited to a delirious activity. 

3. MoiSTUEE. 

286. How mncli moisture the Air contains. — The third constant ingre 
dient of the air is moisture, derived from evaporation upon the earth's 
surface. The quantity which the air will hold depends upon its tem- 
perature, and hence fluctuates greatly. At zero a cubic foot of an 
will hold but "18 of a grain of watery vapor ; at 32° it wiU contain 2-35 
grs.; at 40°, 3*06; at 50°, 4-24; at 60°, 5-82; at 70°, 7-94; at 80°, 
10-73; at 90°, 14-38; at 100°, 19-12 grains, and as the temperature 
goes higher still, the capacity for moisture also increases (308). After 
the air has imbibed its due quantity of vapor, at a given temperature, 
it is then said to be saturated, and will receive no more unless the heat 
be increased. To better appreciate how rapidly the capacity for moist 
ure augments, as the temperature ascends, we will state the propor 
tions in another form. A quantity of air absolutely saturated at 32°, 



> 



158 EFFECTS OF THE CONSTITUENTS OF AIK. 

holds in solution an amount of vapor equal to the ^^^ part of its 
weight; ut 59°, Vo ; at 86°, ^V; at 113°, ^\- and at 140°, -,L. 

287. Conditions of the drying power of the Air. — If, Avhen the air is 
saturated, its temperature falls, a portion of its moisture is precipitated, 
that is, it does not remain dissolved, but appears in drops of dew. 
Thus a cubic foot of air, saturated at 90°, if cooled 10° would deposit 
3*5 <j:rains of Avater. Until it is s^iturated, air is constantly absorbing 
moisture from all sources whence it can procure it. A cubic foot 
of air at 90°, and containing but 8 grains of moisture, is capable of 
absorbing 6"3 more, and this is the measure of its drying power. 
Watery vapor is lighter than the air, and when mingled with it in- 
creases its levity in a degree proportional to its .temperature. This is 
one of the causes of the ascent of breath expired by the lungs, at the 
temperature of the body. In drying-rooms and laundries, if the open- 
ings for the escape of hot air be at the bottom, as the air gets saturated 
with vapor it becomes lighter, and rising, fills the room and stops 
the evaporation. If the opening be at top the loaded air rises aud 
escapes, and the drying will be observed to commence at the bottom. 

288. Moisture in the Air of Rooms — Dew-point. — It has been explained 
that the temperature at which air is saturated, and begins to condense 
its moisture in drops, is called the dew-point (3-i). "When air contains 
so much moisture that its temperature needs to dechne but little be- 
fore water appears, the dew-point is said to he Jiigh; Avhen it must 
lose much heat before drops are produced, its dew-point is loic. Air, 
with a high dew-pomt, is therefore moist, while that with a low dew- 
point is always thirsty and drying. A simple means of finding out 
the dew-point, and ascertaining the drying power of the air, is as 
follows : — Note the temperature of the air by a thermometer, taking 
care that the instrument is not influenced by the radiation of any 
heated body in its vicinity. Then introduce it into a glass of water 
and gradually add a little ice, carefully watching for the first ap- 
pearance of moisture on the outside of the tumbler. The tempera- 
ture at which the deposit commences is the dew-point ; and the 
difference between it and the temperature of the air, expresses its 
drying 'power. If the air is at 60° and moisture begins to be con- 
densed at 40° its drying power is 20 degrees. Mason's hygrometer 
is a little instrument which indicates the dew-point without trouble. 
It has two thermometers, one of which gives the temperature of 
the air, and the bulb of the other, connected constantly with a 
reservoir of evaporating liquid, is kept co(jled, and gives the dew- 
point; so that the amount of humidity in the air is seen at a glance 



MOISTURE — ITS PEESBRVATION IN THE ROOM. 159 

by compai'ing tlie two scales ; — cost, from 3 to 5 dollars. From obser- 
vations made at 'Wasbington tbrougb June, Jnly, August, and Sep- 
tember, from 9 to 3 o'clock of tbe day, tbe dew-point was, on an 
average, 11° below tbe temperature of tbe air, and sometimes more 
tban 20° below. Tbe air is always dampest near tbe ground; a 
difference in beigbt of 60 feet, in tbe same exposure, bas been known 
to make a difference of 10^ degrees in the dew-point. In our bouses, 
we are to imitate as far as possible tbe external conditions of tbe air. 
As tbe temperature of fresbly drawn well water is about 50°, a vessel 
containing it should receive a deposit of moisture when brought into 
our rooms, if they have a temperature above 65°. It is very rare that 
any such deposit is seen in apartments heated by a hot-air furnace, 
•ven if a considerable quantity of water is evaporated. 

289. How donbic Windows affect the moisture of Rooms. — Glass sky- 
lights often drip moisture upon thoso below, and we see it copiously 
condensed in winter upon tbe windows and trickling down tbe panes. 
This is often mistaken for a symptom of abundant humidity in tbe air, 
but it may occur when the air is extremely dry. When, as often 
occurs, air within a room is at 70° or 80°, while just outside the 
window-glass it is down to freezing, or below ; the inner layer of air 
next tbe glass will rapidly deposit its water, and then falling to the 
floor wiU be succeeded by other air (337), so that tbe window acts as 
a perpetual drain upon the moisture of tbe apartment. It is often 
impossible to maintain the air properly humid on this account. Peo- 
jjle are misled by this copious deposit of dew upon the glass, and it is 
hard to convince them that tbe air is deficient in moisture when they 
can see it condensed upon the windows, "We have referred to double 
windows as a means of saving heat, and we might have added that 
they are equally serviceable in summer to exclude its excess of heat ; 
the enclosed air acting just as well to bar oii,t tbe heat of the wann 
season, as to confine it within, in cold weather.* But double win- 
dows also prevent tbe deposit and loss of moisture from the air in 
rooms, and in this respect they are most useful. Glass is not essential 
to their construction, where we require only a diffused light ; white 
cotton cloth stretched upon a suitable frame and rendered impervious 
to air by linseed oil or other preparation, will answer equall}- as well 
for preserving beat, and be much less expensive. 

290. Rate of Evaporation. — When dry air is exposed to a source of 
moisture, a considerable time must elapse before it will become satu- 

* If double windows are to be retained in summer, they cannot be used for airways, 
SS singlo windows are made to do; there must be independent means of ventilation. 



160 EFFECTS OF THE CONSTITUENTS OF AIB. 

rated. The diflfusion of vapor into hot air is much more rapid than 
into that which is lolder, hut it is not at all instantaneous. Mr, 
Daniell observed, that a few cubic inches of dry air, continued to 
expand by the absorption of humidity for an hour or two, when ex- 
posed to water at the temperature of the surrounding air. In cold 
regions there is much less moisture in the air tlian in hot, and less 
in winter than in summer. It is also subject to a regular diurnal 
variation. As the sun warms the air during the day, evaporation is 
increased, and the humid element rises into the atmosphere ; but as it 
declines toward evening, cooling begins, and at night the watery vapor 
again falls, and is deposited upon the earth. We are not to infer that 
because there is an absence of rain, therefore .the air is dry ; on the 
contrary, in long droughts the air is often heavily charged with mois- 
ture. 

291. How moist Air aflTects the System. — The skin relieves the System 
of moisture in two ways ; by insensible perspiration, and by sweating. 
Under common circumstances, the loss is six times greater by the 
former than by the latter process. The skin, as well as the lungs, is 
an excreting organ ; it contains, packed away, some 28 miles of micro- 
scopic tubing, arranged to drain the system of its noxious matters, 
carbonic acid, &c., which, if retained in the body, become quickly in- 
jurious. The perspiration given off in this climate amounts to 20 oz. per 
day, and in hot countries to twice that quantity. Eut air which is al- 
ready saturated with moisture refuses to receive the perspiration which 
is offered to it from the skin and lungs ; the sewerage of the system 
is dannued up. Much of the oppression and languor that even the 
robust sometimes feel in close and sultry days, is due to the obstruc- 
tion of the insensible perspiration by an atmosphere surcharged with 
humidity. Not only are waste matters generated in the system thus 
unduly retained, but malarious poisons introduced through the lungs 
by respiration, are prevented from escaping ; which would lead us to 
anticipate a greater prevalence of epidemic diseases in damp than in 
dry districts. Such is the fact, as we notice in Cholera, which follows 
the banks of rivers, and revels in damp, low situations. Moisture 
joined with warmth is most baneful to the system. The American 
Medical Association report that during the remarkable prevalence of 
Sim-stroke in the city of New York in the summer of 1853, which al- 
most amounted to an epidemic, the heat of the atmosphere was ac- 
companied by great humidity, the dew-point reaching the extraordi- 
nary height of 84°. In Buffalo, in the summer of 1854, the progress 
of cholera to its height was accompanied by a steady increase in at- 



MOISTUBE — CAEBONIC ACID. 161 

mospheric humidity. Air which is warm and moist, has a relaxing and 
weakening influence upon the body. The siroco is invariably charged 
with moisture, and its effects upon the animal economy illustrate but 
in an exaggerated degree the influence of damp warm weather. When 
it blows with any strength, the dew-point is seldom more than four or 
five degrees below the temperature of the air. The higher its tempera- 
ture, the more distressing its effects, owing to the little evaporation it 
produces. This, connected with its humidity, is the principal cause of 
all its peculiarities— of the oppressive heat — of the perspiration with 
which the body is bathed — of its relaxing and debilitating effects on 
the system, and its lowering and dispiriting effects upon the mind. 
— Wtman. Damp air at the same temperature as dry air has a more 
powerful cooling effect, producing a peculiar penetrating chilling feel- 
ing, with paleness and shivering, painfully known to New England 
invalids as accompanying the east winds of spring. 

292. Eflfects of dry Air. — Dry air favors evaporation. By promoting 
rapid transpiration from the pores of the skin, it braces the bodily 
energies and induces exhilaration of the spirits. Cold dry air is 
invigorating and reddens the skin, with none of the distressing symp- 
toms of cold moist air. If very dry, it not only accelerates perspira- 
tion, but desiccates and parches the surface, and deprives the lining 
membrane of the throat and mouth of its moisture so rapidly as to pro- 
duce an uncomfortable dryness, or even inflammation. Dry climates 
which quicken evaporation, are best adapted for relaxed and languid 
constitutions with profuse secretion, as those afflicted with humid 
asthma, and chronic catarrh with copious expectoration. The Har- 
mattan, a dry wind from the scorching sands of Africa, withers, 
shrivels, and warps every thing in its course. The eyes, lips, and 
palate become dry and painful. Yet it seems to neutralize certaia 
conditions of disease. "Its first breath cures intermittent fevers. 
Epidemic fevers disappear at its coming, and smaU-pox infection be- 
comes incommunicable." 

4. Caebonio Aoid. 

293. Physiological effects of Carbonic Acid. — The fourth constant in- 
gredient of the atmosphere is carbonic acid ; a transparent, tasteless, 
inodorous gas. It takes no useful part in respiration, indeed it exists 
in the air in so small a proportion that its effects upon the system are 
inappreciable. Its sources are the combustion of burning bodies, fer- 
mentation and decay, the respiration of animals ; and it is also gener- 
ated within the earth, and poured into the air in vast quantities from 



162 EFFECTS OF THE CONSTITUENTS OF AIR. 

volcanoes, springe, &c. It may be set free more rapidly than it wil 
dissolve away into air ; it then accumulates, as sometimes in weUs, 
cellars, rooms, &c. and becomes dangerous. "When breathed pure, it 
causes suffocation by spasmodically closing up the glottis of the throat. 
"When mixed with air in small quantities, it is admitted to the lungs, 
and then acts as a rapid narcotic poison. The symptoms of poisoning 
by carbonic acid gas are throbbing headache, with a feeling of fulness 
and tightness across the temples, giddiness, palpitation of the heart, the 
ideas get confused and the memory fails. A buzzing noise in the ears 
is next experienced, vision is impaired, and there is strong tendency to 
sleep. The pulse falls, respiration is slow and labored, the skin cold 
and livid, and convulsions and delirium are followed by death. This 
gas has been often employed as a means of suicide. A Son of the 
eminent French chemist, Bertholet, under the influence of mental de- 
pression, retired to a small room, locked the door, closed up every 
crevice which might admit fresh air, carried writing materials to a table 
on which he placed a seconds watch, and then seated himself before 
it, described his sensations, and was found dead upon the floor.* 

294. Effects in small qnantities. — The proportion of carbonic acid ne- 
cessary to produce a poisonous atmosphere is very small ; so much so 
that in attempts at suicide by burning cliarcoal in an open room, the 
people who entered it have found the air quite respirable, although the 
persons sought were in a state of deep insensibility {coma). From 5 
to 8 per cent, of carbonic acid in the air renders it dangerous to 
breathe, 10 to 12 makes it speedily destructive to life. The natural 
quantity in the air is so small that it may be multiplied 20 times before 
it rises to 1 per cent. Air containing one per cent, of this gas is 
soporific, depressing, takes from the mind its cutting edge, tends to 
produce headache, and is most injurious. That proportion of carbonic 
acid which nature has placed in the atmosphere, we assume to be 

* " I light my furnace, and place my candle and lamp on the table with my watch. It 
is now 15 minutes past ten. The charcoal lights with difficulty. I have placed a funnel 
on each furnace to aid the action of the fire. 20 minutes past ten. The funnels fall : I 
replace them ; this does not go to my satisfaction. The pulse is calm, and beats as usual. 
10 h. 30. A thick vapor spreads Itself by degrees in the chamber. My candle seems 
ready to go out. My lamp does better. A violent headache commences. My eyes are 
filled with tears ; I have a general uneasiness. 10 h. 40. My candle is extinguished, the 
lamp still burns. The temples beat as if the veins would burst. I am sleepy. I suffer 
horribly at the stomach ; the pulse beats 40 per min. 10. 50. I am suffocated. Strange 
ide.-is present themselves to my mind. I can hartlly breathe. I shall not live long. I 
have symptoms of madness. lOh. CO. [Here, he confounds the hours with the minutes.] 
I can hardly write; my vision is disturbed; my lamp flickers; I did not believe wc suf- 
fered so much in dying. 10 h. 62 m. [Hero were some illegible characters]." 



THEIR HARMONIOUS AND BENEFICENT ACTION. 1G3 

entiiely inoffensive, but the more it is increased beyond that amount, 
the less it is fitted for respiration. Precisely so with the body. Car- 
bonic acid is continually generated "within it and continually poured 
out from the lungs into the air ; a certain amount in the blood is com- 
patible with health, but if that quantity be slightly increased, it at 
once begins to act as a poison. Any cause, therefore, which hinders 
the escape of this gas from the lungs, tends to accumulate it in the 
blood and pi-oduce injury, and this is exactly the effect, if there be 
considerable carbonic acid in the air we breathe. Its exhalation from 
the lungs is retarded if the outer air already contains more than its 
usual amount of carbonic acid. 

295. Why then does the Air contain Carbonie Aeid? — But if this gas be 
useless, or positively detrimental in animal respiration, why is it made 
a constant and essential ingredient of the atmosphere ? The plaii of 
nature requires it. As it is formed in all animal bodies, and breathed 
out into the air, and also by all combustions, its presence there is un- 
avoidable, while it is the great source of nourishment to the whole 
vegetable world, which drinks it in through innumerable pores in every 
green leaf, and thus keeps the proportion down to the point of safety 
for animals. 

296. Effect of these Ingredients combined. — Such are the constant con- 
stituents of the air, and such, so far as it has been possible to determine 
it, is their separate influence upon man. The efliects of the atmosphere 
we breathe are the resultant of these agents acting together. We see 
that it exerts an all-controlling influence upon the human constitution. 
To say that it is useful or important, gives us no adequate conception 
of the facts ; it is the first condition of vital activity — what the stream 
is to the water-wheel or fire to the steam-engine — the immediate 1m- 
peUing power of life. Any one of its elements breathed alone would 
be fatal ; any other proportions than those in which they are com- 
mingled would be dangerous or deadly. Its elements taken alone are 
poisonous and excoriating, but properly mingled and neutralized, how 
bland, how balmy, how innocent they become. Pressing upon us Avith 
the weight of tons, bathing the sensitive breathing passages — distend- 
ing the filmy membranes of the air cells, flashing through into the 
blood and swept forward to the inmost depths of the system, corroding 
and consuming in its progress the living parts — and yet with such 
marvellous delicacy are all these things accomplished, that we remain 
profoundly imconscious of them. Unspeakable indeed are these har- 
monics of life and being, and how adorable the Power, Wisdom and 
Love from which they emanate. 



]G4 EFFECTS OF THE CONSTITUENTS OF AIR. 

5. OZOXE AND ElEOTEIOITT. 

297. Ozone in the Air. — Our view of the properties of the atmo- 
sphere would be incomplete without reference to these agencies. At- 
tention has latterly been drawn to the interesting and significant fact 
that the chemical elements are capable of existing in different states, 
with widely difltei'ent properties and powers. "We see this in the case of 
cai'bon, which assumes several states, as charcoal, lampblack, diamond. 
Sulphur, phosphorus, and indeed many of the other elements are found 
capable of this change of state, wiich is known as aUotropism. It has 
been discovered also that the remarkable element oxygen has its double 
condition, its ordinary state and another of extreme activity, in which 
it seems to acquire new energies ; in this heightened form of action it 
is called ozo?ie. It may be readily changed from the common to the 
superactive state, acquiring bleaching and oxidizing energies which it 
had not before. Ozone is extensively formed in the atmosphere, by the' 
operations of nature, although under precisely what circumstances we do 
not know. It is found more abundantly in some localities than in 
others, and may be generally recognized in air which has swept over 
the ocean, although usually absent in that which has traversed large 
tracts of land. There has been much speculation as to how the air is 
affected by its presence, in relation to health and disease. It is said 
that when present in excess diseases of the lungs, especially influenza, 
prevail ; when deficient, fevers and aU those diseases which are sup- 
posed to depend upon a kind of fermentation in the blood are com- 
mon, — it being thought that ozone oxidizes or burns away the exciting 
fermentable matter, thus acting as a purifying agent. It has been 
staled that in cholera ozone is entirely absent from the air. 

298. Atmospheric Electricity. — "I cannot tell," says Dr. Faraday, 
" whether there are two fluids of electricity, or any fluid at all ;" such 
is our profound uncertainty in relation to this mysterious agent. Yet 
it is commonly assumed to be a subtle fluid, distributed through all 
substances, and lying buried beneath their surfaces in a condition of 
equilibrium, or rest. Various causes may disturb this state, producing 
electrical excitement, when the fluid is supposed to accumulate in 
some substances to excess, which are then said to be positively electri- 
fied, — while in others it is deficient, and these are negatively electrified. 
Some substances, as the metals, allow electricity to pass through them 
freely ; these are called good conductors; others refuse it a ready passage, 
and are termed non-conductors, as silk, glass, air. When from any cause 
exciteaient has taken place, and a body has been charged with electri- 



ELECXRICITr — ATMOSPHERIC CONTAMINATIONS. 165 

city, or robbed of it to a certain degree, there is an escape ; if a good 
conductor be presented to it, it flows off quietly ; if a bad conductor, it 
dashes through it, producmg fire, light sound, and perhaps violent 
rupture {disruptive discharge). The friction of unlike bodies against 
each other creates electrical excitement. If we slide rapidly over a 
carpet, the body becomes so excited that it may yield a spark which 
will light the gas. The friction of masses of air, of different temper- 
atures, or containing different degrees of moisture, by rubbing against 
each other, or grinding against the earth, developes electricity. So, 
also, does evaporation. If a saiacer of water be suspended by non- 
conducting silk cords (insulated), evaporation goes on as usual at first, 
but is soon checked. It gives off positively electric vapor, while the 
saucer remains negatively electrified. If it be connected with the 
ground by a conductor, active evaporation is resumed. Combustion 
produces electricity ; the escaping carbonic acid being positive, while 
the burning body is negative ; the vapor of the expired breath is also 
positive. The air is generally electrified positively, especially in clear 
weather ; but during the fall of rain, fogs, snow, and storms, it may be 
negative. The electricity of the atmosphere appears to have a daily 
ebb and flow, like the tides of the sea, twice in every 24 hours. It is 
feeble at sunrise, increases in intensity during the forenoon, declines 
again in the afternoon, until about two hours before sunset ; it then 
advances until perhaps two hours after sunset, and again diminishes 
until morning. It has become fashionable, latterly, to ofler electricity 
in explanation of all obscurities, material and spiritual. Beyond doubt 
it is profoundly involved in the phenomena of our being, but we as 
yet understand but little about it. In connection with tLe air, we can 
only say, that when it is clear, and electricity is rapidly developed, the 
spirits are more buoyant, and the feelings more agreeable, than when 
the atmosphere is in the opposite state. 

III.— CONDITION OF AIR PROVIDED BY NATURE. 

299. Impurities of tlie external Air.— There are natural causes which 
tend to make the atmosphere impure, but they act with variable in- 
tensity in different localities. Anim.al respiration and combustion exert 
a contaminating influence upon the atmosphere, but considering its 
vast mass, the general effect is but trifling, and besides is perfectly 
neutralized by growing vegetation, which evermore absorbs from the 
air carbonic acid, and returns to it pure oxygen in the daytime. The 
decay of organic matter, vegetable and animal, generates numer- 



166 CONDITION OF AIR PROVIDED BY NATLIRE. 

ous substauces which are prejudicial to health. Liebig has lately 
shown that ammonia from these sources is continually present in 
the air. Its quantity is so minute that it cannot be directly de- 
tected, but it may be traced in rainwater, having been washed 
out of the air in its descent (37'1). The exhalations and effluvia 
arising from active decomposition in wet lands, swamps, marshes, 
&c., especially in hot seasons and localities, are prolific sources 
of disease. Minute microscopic germs, both vegetable and animal, 
exist in the atmosphere, and the course of winds has been tracked 
across oceans by the peculiar organic dust which they carried. 
Not only do plants and flowers exhale continually their peculiar fra- 
grances, but even mineral matters and earths have also their odors, which 
rise and mingle with the air. Indeed, we must conceive of the air as 
the grand reservoir into which all volatile matters escape. Professor 
Graham contends that malarious and contagious bodies are not strictly 
gaseous, but are highly organized particles of fixed or solid matter, 
which find their way into the atmosphere, like the pollen of flowers, 
and remain for a time suspended in it. The inconceivable minuteness 
of exhalations diffused through the air, which are yet sufliciently 
active to impress the senses, is forcibly illustrated by the following 
fact, which we give on the authority of Dr. Oaepenter. '' A grain 
of musk has been kept freely exposed to the au' of a room, of which 
the doors and windows were constantly open for a period of ten years, 
during all which time the air, though constantly changed, was com- 
pletely impregnated with the odor of musk ; and yet, at the end of 
that time, the particle was found not to have sensibly diminished in 
weight." 

300. Effects of Exposnrc, Foliage, and Soil. — The salubrity of the ex- 
ternal air is influenced by elevation, trees, and soil. The exposed hill- 
top ensures atmospheric purity. It is often surprising what effect 
a small difference in the elevation has upon the healthfulness of a par- 
ticular spot. A rise of 16 feet within 300 yards has been known to 
produce an entire change from a relaxing to a bracing air. The lower 
place was completely enveloped in foliage and without drainage, while 
the higher was comparatively free from trees, and besides, had a good 
fall for surface-water and sewerage. Dense foliage around a dwelling 
may be injurious, by causing dampness and stagnation of air, especially 
if the situation be protected from winds. If the ground be loaded 
with putrefying matter and soaked with refuse water, the air above it 
cannot be pure. The ground below and around the dwelling should 
be dry. A soil absorbent and retentive of moisture, always damp, is 



IMPURITIES NEAR THE GROUND AT NIGHT. 167 

unfit to live on unless thoroughly drained. Sand or gravelly ground 
is best, provided it bo not locked in by a surrounding clay basin, with 
no outlet for the rainfall. 

301. Cause of the onwholesomeness of Night Air. — There is ground for 
the common belief that night air is less healthful than that of the day. 
It is known that the deadly tropical fevers affect persons almost only 
during the night. Yet the poisonous miasms ft'om the rotting substan- 
ces of the ground which cause those fevers, is produced much fester 
during the intense heat of the day than in the colder night. But in 
the daytime, under the hot tropical sun, the air heated by contact 
with the burning ground expands and rises in an upward current, thus 
diluting and carrying away the poisonous malaria as fast as it is set 
free. The invisible seeds of pestilence, as they ripen in the festering 
earth, are lifted and dispersed in the daytime by solar heat ; but as no 
such force is at work at night, they then accumulate and condense in 
the lower layer of the atmosphere. Now although fatal fever poison 
may not be generated, yet decomposition of vegetable matter yielding 
products which are detrimental to health take place every where upon 
the surface of the ground ; and though dissipated during the day, they 
are concentrated and confined so close to the earth at night as to affect 
the breathing stratum of the air. 

302. Upper Rooms least affected by Night Air. — It wiU hence be seen 
that -the different stories of a house are differently related to this 
source of injury : the upper ones being situated above the unwhole- 
some zone, are most eligible for sleeping chambers, whde the ground- 
floor is more directly exposed to the danger. Dr. Rusn states, that 
during the prevalence of yellow fever in Philadelphia, those who oc- 
cupied apartments in the third story were far less liable to attack than 
those who resided lower. Low one-story houses, in which the inhab- 
itants sleep but three or four feet from the ground, and are therefore 
directly exposed to the terrestrial exlialations, must be considered 
more objectionable than loftier sleeping apartments. Sleeping in low 
rooms is perliaps worse in the city than in the country. 

303. The Atmosphere Self-purifying.— In aU healthy localities the pro- 
portion of impurities is so small tliat their effect is imperceptible. 
When noxious exhalations are set free from any source, they are dif- 
fused through the vast volume of the atmosphere, so as not to be 
detectable by the most refined means of chemistry. The law of 
gaseous diffusion, aided by winds and storms, secures dispersion and 
universal intermixture. Oxygen finally takes effect upon these baneful 
emanations, destroying and biu-ning them as truly as if they had been 



168 SOURCES OF IlirURK AIK IN DWELLINGS. 

consumed in a furnace. The atmosphere thus secures its own puri- 
fication ou the grandest scale, and its vital relation to animal life re- 
mains undisturbed. 

304. Air within Doors. — But when we enter a dwelling the case is 
altered. It is as if the boundless atmosphere had ceased to exist, or 
had been contracted within the walls of the apartment we occupy. 
Causes of impurity now become a matter of serious consideration. 
They are capable of affecting, in the most injurious manner, the little 
stock of air in which we are confined ; and it is therefore, on every 
account, important that we have a clear idea of the nature and extent 
of the common causes which vitiate the air of our dwellings. 

IV.-SOURCES OF IMPURE AIR IN DWELLINGS. 

305. Breathing and Combustion. — By breathing, the burning of fuel 
and combustion for light, large quantities of oxygen are removed from 
the air, while at the same time carbonic acid in nearly equal bulk 
takes its place. In the case of fuel, if the combustion is perfect, the 
air that has been changed is immediately removed up chimney by the 
draught. But not so in respiration and illumination ; the air spoiled 
by these processes remains in the room, unless removed by special 
ventilating arrangements. 

30G. Leakage of bad Gases from Heating Apparatus. — While, in point 
of economy, stoves are most advantageous sources of heat, yet in their 
effects upon the air they are perhaps the worst. We saw that in the 
stoves called air-tight^ the burning is carried on in such a way that 
peculiar gaseous products are generated (121). These are liable to 
leak through the crevices and joinings into the room. Carbonic oxide 
gas is formed under these circumstances, and recent experiments liave 
shown that it is a much more deadly poison than carbonic acid. The 
slow, half-smothered burning of these stoves requires a feeble draught, 
which does not favor the rapid removal of injurious fumes. Besides, 
carbonic acid being about half as heavy again as common air, must be 
heated 250° above the surrounding medium to become equally light, 
and still higher before it will ascend the pipe or flue. If the com- 
bustion of the fuel is not vivid, and the draught brisk, there will be 
regurgitation of this gaseous poison into tlie apartment. Dr. Ukb 
says, " I have recently performed some careful experiments upon this 
subject, and find that when the fuel is burning so slowly as not to heat 
the iron surface above 250° or 300°, tJiere is a constant deflux of car- 
Ionic acid into the room.'''' Probably all stoves, from their imperfect 



HOW AIR IS ALTERED ]?Y HEAT. 109 

fittings, are liable to this bad result. Hot-air furnaces, also, have the 
same defect. They are cast in many pieces, and however perfect the 
joinings may be at first, they cannot long be kept air-tight, m conse- 
quence of the unequal contraction and expansion of the difierent parts 
under great alterations of heat. Combustion products are hence 
liable to mingle with the stream of air sent into the room. 

307. Air affected by Hot-iroa Surfaces. — But if stoves become a source 
of contamination to the air at low temperatures, neither are they free 
from this objection when made hotter ; at high heats (and they are 
often red-hot), they seriously injure it in other ways. It is well known 
that iron highly heated causes disagreeable effects upon the air of 
rooms, producing a sensation ascribed to lurnt air, but the nature of this 
change is not fully understood. The common method of explaining it, 
that the iron decomposes the air and robs it of oxygen, is in no degree 
satisfactory, as the quantity of oxygen thus removed must be extremely 
small, and besides, a portion of this very small amount comes from 
the decomposition of atmospheric moisture, its hydrogen being set 
free. The minute particles of dust, myriads of which fill the air, as 
seen when a ray of light is admitted into a darkened room, and which 
consist of all kinds of vegetable and animal matters, settle upon the 
hot stove, and are roasted or burnt with the escape of gaseous impu- 
rities. In the stove metal itself there is always, beside the cast-iron, 
more or less carbon, sulphur, phosphorus and arsenic, and it is possible 
that the smell of air, passed over it in the red-hot state, may be owing 
to the volatilization or escape of some of these ; because it is to be re- 
membered that a quantity of noxious efiluvia, too small to be seized 
and measured by chemical means, may yet afiect the sense of smell 
ajid the pulmonary organs. 

308. Composition of Air altered by heating it. — It is a capital advan- 
tage of the methods of warming by fireplaces and grates — simple ra- 
diation — that they do not heat the air : it remains cool while the 
heat rays dart through it to warm any objects upon which they fall. 
The sun pours his floods of heat through the atmosphere without 
warming it a particle. Air is made to be breathed, and we again dis- 
cover Providential Wisdom in the arrangement by w^hich the sun 
warms us, without disturbing, in the slightest degree, tbe respiratory 
medium. But if we heat the air itself, we at once destroy the natural 
equilibrium of its composition, and so change its properties that it be- 
comes more or less unpleasant and prejudicial to health. We liave 
noticed the bad eflfects upon the system of dry heated air, and it was 
shown that the state of dryness does not depend upon the actual 

8 



170 



SOURCES OF IMPURE AIR IN DWELLINGS. 



amouut of moisture present, but upon the temperature, 
same quantity of aqiie- _, „ 

ous vapor, it "will be 
moist and humid at a 
low temperature, while 100° 
at a high one it will be ^o 



With the 




The length of the bars indicates the relative propor- 
tions of moisture that a cubic foot of air will nofd at 
the different temperatures. 



parched and greedy of 
■water. The accompa- 
nying diagram (Fig. Yl) 
exhibits the relative 
amount of moisture that 
air contains when satur- 
ated at the temperatures 
mentioned. Suppose that air at 32° be heated to 100° (and it often is 
much higher), and be then thrown into the room. The difference in 
the length of the bars opposite these two numbers expresses its de- 
ficiency of moisture, and hence its drying and parching power. Air 
thus changed is apt to produce unpleasant feelings and painful sensa- 
tions in the chest, -which are often attributed to too great heat. " In 
very dry air the insensible perspiration will be increased, and as it is 
a true evaporation it will generate cold proportional to its amount 
(69). Those parts of the body which are most insulated in tlie air, 
and furthest from the heart, wUl feel this refrigerating influence most 
powerfully ; hence that coldness of the hands and feet so often expe- 
rienced. The brain being screened by the skull from this evaporating 
influence, will remain relatively hot, and wiU get surcharged besides 
with the fluids which are expelled from the extremities, by the con- 
traction of the blood-vessels caused by cold." In close rooms, not 
well ventilated, stoves exert this baneful influence upon the air in an 
eminent degree. This objection lies against heated air, no matter how 
heated. Stoves and air-furnaces, with their red-hot surfaces, are un- 
doubtedly worse for the air than hot-water apparatus, which never 
Bcorch it ; yet they, too, may pour into our apartments a withering 
blast of air at 150°, which may be potent for mischief. The only way 
that hot-air can be made healthful and desirable is by an effectual plan 
of artificial evaporation, which will be noticed among the means of 
preserving atmospheric purity (347). 

309. Contamination of Air from the Ilnmau Being. — It is a common 
belief that the human system is distinguished by its vital power of re- 
sisting, during life, the physical agents which would destroy it ; but 
that after death it is abandoned to these forces, and falls quickly into 



EXHALATIONS FEOM THE LIVING BODY. 171 

putrefaction. This is an error. Under the influence of physica. 
agency decomposition is constantly going on throughout the body, and 
is indeed the fundamental condition of its life (624). There is the 
same decay and chemical decomposition taking place in the animal 
fabric during life as after death ; the difference being, that in the dead 
body the decomposing changes speedily spread throughout the mass, 
while in the living system they are limited and regulated, and pro- 
vision is made for the incessant and swift expulsion of those eflete 
and poisonous products of change, which if retained within the organ- 
ism for but the shortest time, would destroy it. Streams of subtile 
and almost intangible putrescent matter are, all through life, exhaling 
from each living animal body into the air. The fluid thrown from the 
lungs and skin is not pure water. It not only holds in solution car- 
bonic acid, but it contains also animal matter^ the exact nature of 
which has not been determined. From recent inquiries, it appears to 
be an albuminous substance in a state of decomposition. If the fluid 
be kept in a closed vessel, and be exposed to an elevated temperature, 
a very evident putrid odor is exhaled by it. Leblano states that the 
odor of the air at the top of the ventilator of a crowded room, is of 
so obnoxious a character that it is dangerous to be exposed to it, even 
for a short time. If this air be passed through pure water, the water 
soon exhibits all the phenomena of putrefactive fermentation. 

310. Dr. Faraday's Testimony npon this point. — "Air feels unpleasant 
in the breathing cavities including the mouth and nostrUs, not merely 
from the absence of oxygen, the presence of carbonic acid, or the ele- 
vation of the temperatui-e, lutfrom other causes depending on matters 
communicated to it from the human leing. I think an individual may 
find a decided difference in his feelings when making part of a largo 
company, from what he does when one of a small number of persons, 
and yet the thermometer give the same indication. "Wlien I am one 
of a large number of persons, I feel an oppressive sensation of closeness, 
notwitlistanding the temperature may be about 60° or 65°, which I 
do not feel in a small company at the same temperature, and which I 
cannot refer altogether to the absorption of oxj^gen, or the inhalation 
of carbonic acid, and probably depends upon the effluvia from the many 
present ; but with me it is much diminished by a lowering of the tem- 
perature, and the sensations become more like those occurring in a 
small company." 

311. Air of Bedrooms. — The escape of offensive matters from tlic liv- 
ing person becomes most obvious when from the pure air we enter an 
nnventilated bedroom in the morning, where one or two have slept 



172 SOURCES OF IMPURE AIR IN DWELLINGS. 

the night hefore. Every one must have experienced the sickening anil 
disgusting odor upon going into such a room, though its occupants 
themselves do not recognize it. The nose, althougli an organ of ex- 
quisite sensibility, and capable of perceiving the presence of offensive 
matters where the most delicate chemical tests fail, is nevertheless 
easUy blunted, and what at the first impression feels pre-eminently dis- 
gusting, quickly becomes inoftensive. Two persons occupying a bed for 
eight hours, impart to the sheets by insensible perspiration, and to the 
air by breathing, a pound of watery vapor charged with latent animal 
poison. "Where the air in other inhabited rooms is not often changed, 
the water of exhalation thus loaded with impurities, condenses upon 
the furniture, windows, and walls, dampening their surfaces and run- 
ning down in unwholesome streams, 

312. Purity the Intention of Natnre* — Yet we are not to regard the 
himian body as necessarily impure, or a focus of repulsive emanations. 
The infinite care of the Creator is seen nowhere more conspicuously 
than in the admirable provision made for the removal of waste matters 
from the system, the form in which they are expelled, and the prompt 
and certain means by which nature is ready to make them inoffensive 
and innoxious. " The skin is not only," as Biohat eloquently observes, 
" a sensitive limit placed on the boundaries of man's soul, Avith which 
external forms constantly come in contact to establish the connections 
of his animal life, and thus bind his existence to all that surrounds 
him ; " it is at the same time throughout its whole extent densely 
crowded with pores, through which the waste substances of the system 
momentarily escape in an insensible and inoffensive form, to be at once 
dissolved and lost in the air if this result he allowed. It is not by the 
natural and necessary working of the vital machinery that the air is 
poisoned, but by its artificial confinement and the accumulation of 
deleterious substances. If evil results, man alone is responsible. 

313. Other sources of Imparity. — Gaseous exhalations of every sort 
escape from the kitchen, and are diffused through the house as their 
odors attest, and the darkening of walls and wood-work painted with 
white lead shows that poisonous sulphuretted hydrogen from some 
Bource has been thrown into the air, its sulphur combining with the 
lead and forming black sulphuret of lead.* From the imperfect com- 
bustion of oil and tallow for lighting, and the defective burning of gas 
jets there arise emanations often most injurious to health. The vapor 
of a smoky lamp, if disengaged in small quantities, and the fumes of 
the burning snutF of a candle, may fill the room with disgusting odora 

♦ White zinc paint does not thus turn black. 



INFLUENCE OF CELLARS AND EASEMENTS. 1*73 

and excite severe headache. It may be well here to correct the com- 
mon follacy that cold air is therefore pure, aud that apartments need 
less ventilation in winter than in summer. People confound coolness 
with freshness, and disagreeable warmth with chemical impurity ; 
whereas these properties have necessarily nothing to do with each 
other. Cold air may be irrespirable from contamination and warm air 
entii-ely pure. 

314. Poisonous Colors on Paper Hangings. — Attention has lately been 
called to the poisonous influence of green paper hangings upon the air. 
Cases are mentioned of children poisoned by chewing green colored 
hanging paper, and of persons sickened by breathing air in rooms in 
which certain green papers have been mounted. The basis of the bright 
green colors used for staining paper-hangings is the poisonous arsenite 
of copper, a combination of arsenic and copper. This, however, is not 
volatile, and does not create poisonous fumes or vapors, unless perhaps 
by being dusted fine particles are loosened and set afloat in the air. 
Nevertheless, though it do not vaporize and get into our systems 
through the lungs, arsenite of copper is a deadly poison, and when 
spread over paper-hangings, utterly spoils them/t>r dietetical purposes^ 
either for children or adults. Professor Johnsox, of New Haven, states 
that the most beautiful of all green pigments is the aceto-arsenite of 
copper, and that this compound, in damp weather and humid situations, 
exhales deadly poisonous vapors supposed to contain arsenuretted 
hydrogen. This gentleman has given an account of a family poi- 
soned by sleeping in a room where the paper was colored with this 
pigment. 

815. Foal Air generated in Cellars, — The air in our houses is also liable 
to contamination from various organic decompositions, if vigilant 
precaution is not taken to prevent it. Cellars are commonly con- 
verted into reservoirs of pernicious airs, by the reprehensible custom 
of using them as receptacles for the most perishable products. But 
even where large masses of organic matter are not left to undergo 
putrefactive decay, and generate unwholesome miasms, serious injury 
is liable to occur from the damp and stagnant air of basements and 
cellars. It is not necessary that the lower spaces of a house should 
be half filled with rotting garbage to generate foul air. The surface 
of the earth is filled with decomposable substances, and whenever air 
is confined in any spot in contact with the ground, or any changeable 
organic matter, it becomes saturated with various exhalations which 
are detrimental to health. If air is to be confined, unless it is so 
sealed up as to touch nothing but dry, glassy or mineral substances, 



174 ^[ORBID AND FATAL EFFECl-S OF IMPURE AIR. 

it will certainly degenerate. Even dry rooms and closets in the upper 
part of the house, become mouldy and musty to a most disagreeable 
extent, if not often aired. To be pure and healthy, air requires con- 
tinual circulation ; but cellars are very rarely either ventilated or 
made absolutely dry by water-proof walls or floors. They are usually 
damp, cold, uncleanly, and mouldy. " The noxious air generated in 
cellars, basements, and under-floor spaces, reaches the inhabitants of 
upper apartments in so small quantities, that instead of producing 
any marked and sudden process of disease, it operates rather as a 
steady tax upon their income of health ; so uniform in its depressing 
effects as not to be appreciated. Y^t many an invalid, who fancies 
himself improved by a change of air, in going to another residence, 
is really relieved by escaping the mouldy atmosphere which comes 
from beneath his own ground-floor." * 



V. MORBID AND FATAL EFFECTS OF IMPURE AIR. 

316. Sources of danger in Breathing — The constituent of the atmo- 
sphere are mingled in such perfect proportions, that its temper is ex- 
actly suited to the necessities of the healthy system ; any alteration 
in its composition, therefore, however slight, must result in physi- 
ological disturbance. So direct is the access that respiration affords 
to the inmost recesses of the body, that any gas mingled with the re- 
spired air, is at once admitted, and takes prompt control of the system. 
When aliment is taken into the stomach, it is submitted to a long 
process of preparation and sifting, before it can gain admission to the 
blood, those parts which are useless or obnoxious being rejected; 

* "The reports of the Eegistrar-Genera of England disclose to us some very startling 
facts in reference to the slow influences of different states of air in affecting length of 
life. If any one were to select from among all the different occupations the healthiest 
men of a nation, he would probably choose the farmers and the butchers. Both arv 
usually stout in fi'ame, and ruddy in complexion. Both are actively employed, have 
plenty of exercise and abundance of food. In one point, therefore, their circumstances 
widely differ. The farmer breathes the pure air of the country ; the butcher inhales the 
atmosphere of the shambles and the slaughter-house, tainted with putrefying animal 
effluvia. The result is an instructive lesson as to the value of pure air. The rate of deaths 
itated among the farmers, between the ages of 45 and 55, was 11 'Od per thousand 
^annually). The butchers at the same age died at 2.3-1 per thousand, so that their mor- 
tality is about double that of the farmers. These two classes, indeed, occupy nearly tho 
extremes of the table of mortality. Tho farmer is the healthiest man on the list, while 
there is but one worse off than tho butcher — the innkeeper. Any one who knows how 
large a proportion of taverns are mere grogshops, reeking with impurities and environed 
in tilth, will not bo surprised that the mortality among this class ascends to SSSi in the 
•housand." 



IT PREPARES THE WAY FOR PESTLLENCE. IVS 

but tliu lungs exercise no sucli protective or selective power, they 
cannot guard the system by straining the air, or barring out its in- 
jurious gases. Besides, air both pure and impure is ahke transparent 
and invisible, so that the eye cannot detect the difference. Tlie 
causes of vitiation are also gradual and insidious in their action, 
so that their effects steal imperceptibly over the system. Unliko 
heat, deleterious air announces its presence by no sensation ; indeed, 
its effects are of that stupefying kind that makes a person insensible 
to them. A bedroom, as we before remarked, may be so foul from 
^oathsome exhalations, as to nauseate a person who enters it from the 
pure air, and yet its inmates will feel quite unconscious of any thing 
di-jagreeable. Without intelligent and thoughtful precaution, there- 
fore, we are constantly liable to the evil effects of foul air, and to im- 
minent danger from various forms of disease. 

317. The System prepared to receive Contagion. — Eespiration of im- 
pure air, is a prolific source of disease, which appears in numerous 
forms and all degrees of malignity. The effect of breathing a con- 
fined and unrenewed atmosphere, is not only to taint the air, but by a 
double influence, to taint also the blood. It is an ofiice of oxygen in 
the body, as we have seen, to throw the products of waste into a 
soluble state that they may be readily excreted, but if its quantity be 
diminished in the air, this work is impei'fectly performed in the body ; 
and the vital current is encumbered with putrescent matter. The 
increase of carbonic acid in the air, by offering a barrier to exhalation 
from the lungs, conspires to the same result. Accumulation of these 
morbid products in the blood, greatly heightens its susceptibility of 
being acted upon by atmospheric malaria, the causes of epidemics. 
The blood is supposed, under these circumstances, to acquire a fer- 
mentable state, forming, as it were, a ready prepared soil for the seeds 
of infection. Atmospheric malaria seem not capable alone of producing 
ei)idemic disease. From those in real robust health, with perfect 
sanative surroundings, the arrows of contagion rebound harmless. 
The miasmatic poison must find some morMdity in the system to co- 
operate wit\ — some unhealthy condition induced by intemperence or 
debauchery, bad food or drink, bodily exhaustion, mental depression, 
or the discomforts of povei'ty — upon which it may take effect. But 
of all these predisposing agencies, none invite the stalking spectre of 
pestilence with so free and deadly a hospitality, as corrupt, con 
laminated air. 

318. IHastration in the case of Cholera. — Of the tendency of an at- 
mosphere charged with the emanations of the human body^ to favor 



176 MOKBID ANB FATAL EFFECTS OF IMPUKE AIR. 

the spread of contagious disease, the illustrations that might be quoted 
are inuumcrahle. Take an instance of cholera, for example. It is 
■well known to those who have had the largest opportunities of study- 
ing the conditions which predispose to this malady, that overcrowding 
is among the most potent. In the autumn of 1849, a sudden and 
violent outbreak of cholera occurred in the workhouse of the town 
of Taunton (England), no case of cholera having previously existed, 
and none subsequently presenting itself among the inhabitants of 
the town, though there was considerable diarrhoea. The building 
was badly constructed, and the ventilation deficient ; but this was 
especially the case with the school-rooms, tTiere leing only about 68 
cubic feet of air for each girl, and even less for the boys. On Nov. 3d 
one of the inmates was attacked with the disease ; in ten minutes 
from the time of the seizure, the sufferer passed into a state of hope- 
less collapse. AVitliin the.space of 48 hours, from the first attack, 42 
cases and 19 deaths took place; and in the course of one week, 60 
of the inmates, or nearly 22 per cent, of the entire number were 
carried off; whilst almost every one of the survivors suflered more 
or less, from cholera or diarrhoea. Among the fatal cases were those 
of 25 girls and 9 boys, and the comparative immunity of the latter, not- 
withstanding the yet more limited dimensions of their school-room, 
affords a remarkable confirmation of the principle we are indicating, 
for we learn that ^'■although good and obedient in other respects, the 
boys could not be Tcept from breaking the windows,''^ so that many of 
them probably owed their lives to the better ventilation thus established. 
In the jail of the same town, in which every prisoner was allowed 
from 800 to 900 cubic feet of air, and this continually renewed by an 
effcient system of ventilation, there was not the slightest indication 
of the epidemic influence. (Dr. Caepentee.) It is in confined spaces 
thus charged with putrescent bodily exhalations, that pestilence revels ; 
they resemble in fatality those localities where the air is poisoned 
by effluvia from foul drains, sewer-vents, slaughter-houses, and manure 
manufactories. 

319. Fevers originate in Impnre Air. —As with cholera, so also with 
fevers ; foul air not only augments their malignity, but also calls them 
into existence. "Writers on pestilence, observes Dr. Geiscom, note two 
distinct species of virus applied to the body, through the medium of tho 
air. First, that arising from the putrefaction of dead animal and vege- 
table matter — the accumulations of filth around dwellings and in cities, 
and the exhalations of swamps, grave-yards, and sewers, called marsh 
miasm. This is supposed to give rise to yellow, remittent, bilious, 



IT PRODUCES FEVERS AND SCROFULA. Ill 

and intermittent fevers, dysentery, and perhaps also cholera. And 
second, exhahations from the human hody, contined and accumuhited 
in iU -ventilated habitations, sometimes termed typhoid miasm, and 
which usually gives origin to common typhus and low nervous fevers. 
It would thus appear, that the very type and character of febrile 
disease is determined by the kind of impurity which is breathed. 
Prof. Smith, of New York, says, "Let us suppose the circumstances 
in which typhus originates, to occur in summer, such as the crowd- 
ing of individuals into small apartments badly ventilated, and ren- 
dered offensive by personal and domestic filth ; these causes would 
obviously produce typhus in its ordinary form. But, suppose there 
exist at the same time, those exhalations which occasion plague, and 
yellow fever, or remittent and intermittent fevers; under such cir- 
cumstances we would not expect to see any one of those diseases fully 
and distinctly formed, but a disease of a new and modified character. 
It is, therefore, beyond probability that a few deleterious gases are 
quite sufficient to produce an infinite variety of pestilential and con- 
tagious maladies." 

320. Scrofula, or Struma, the consequence of Impure Air. — There is a 
diseased condition of body known as scrofulous or strumous^ which 
manifests itself in various forms, and in all parts of the system. It 
seems to be a result of deficient nutrition; that is, not a want of 
material for nutricious purposes, but a failure of power to produce 
healthy and perfect tissue from the elements of food. Various causes 
have been assigned as tending to produce scrofulous habits of body, 
such as hereditary tendency, bad diet, depressing passions, too late, 
too early, or in-and-in marriages, sedentary occupations, want of ex- 
ercise, deficient clothing, bad water, &c., and these, under different cir- 
cumstances, may each contribute to the result ; but imperfect respira- 
tion is probably the most efficient and universal cause. An eminent 
French Physician, * who has made this subject a matter of extensive 
study, says, "Invariably it will be found on examination, that a truly 
scrofulous disease is caused by a vitiated air, and it is not always neces- 
sary that there should have been a prolonged stay in such an atmosphere. 
Often a few hours each day is sufficient, and it is thus that persons may 
live in the most healthy country, pass the greater part of the day in 
the open air, and yet become scrofulous, because of sleeping in a 
confined place, where the air has not been renewed." The same ob- 
server goes further, and affirms that the repeated respiration of the 
same atmosphere, is a primary and efficient cause of scrofula, and 

♦ M. Bauuoloquk. 

8* 



178 MOKBID AND FATAL EFFECTS OF rMPUKE AIR. 

that, " if there be entirely pure air, there may be bad food, bad cloth- 
ing, and want of personal cleanliness, but that scrofulous disease can- 
not exist." In 1832, at Norwood School in England, where thera 
were 600 pupils, scrofula broke out extensively among the children, 
and carried off" great numbers. This was ascribed to bad and inef- 
ficient food. Dr. Arnott was employed to investigate the matter, and 
immediately decided that the food "was most abundant and good," 
assigning " defective ventilation, and consequent atmospheric im- 
purity " as the true cause. 

321. Consamption indnced fey Impure Air. — When scrofula localizes 
itself in the lungs, there is 2ndmo)iar-i/ or Utlercrilar consttnqytion. The 
essence of the nutritive process consists in the vital transformation of 
albumen (678) into fibrin and organized tissue. Now the tubercles 
which in this disease make their appearance in the pulmonary 
organs, consist of crude, coagulated, half organized masses of albumen 
— the abortive products of incomplete nutrition. In this manner, 
bad air, by producing the strumous condition, becomes a cause of con- 
sumption. It seems natural to expect that the organs with which 
the foreign gaseous ingredients of the atmosphere come more im- 
mediately into contact, and whose blood-vessels they must enter on 
their passage into the system, should feel, in a distinctive manner, 
their noxious influence ; and this expectation is strengthened by 
observation, and experiment upon both men and animals. It has 
been observed that when individuals habitually breathe impm-e air, 
and are exposed to the other debilitating causes which must always 
influence, more or less, the inhabitants of dark ill- ventilated dwellings, 
scrofula, and consumption, as one of its forms, are very apt to be 
engendered. 

322. State of the Air iiiflnenccs infant Mortality. — The same malign in- 
fluence of the air of unventilated rooms is seen in the mortality of 
infants. That the new-born and tender chUd should be infinitely sus- 
ceptible to the influence of contaminated air is what we might well 
expect. We are, therefore, not surprised, that in the foul and stifling 
air of Iceland habitations, two out of three of all the children should 
die before twelve days old. Opportunities have been aftorded in hos- 
pitals, to compare the effects of pure and vitiated air, and it has been 
invariably found that a neglect of atmospheric conditions was accom- 
panied by high rates of infant mortality, which promptly disappeai'ed 
vvith the introduction of eflicieut ventilation. " On the imagination of 
mothers, educated as well as ignorant, the feeling still seems to be 
Btercotypcd, that the free, pure, unadulterated air of heaven falls upon 



IT BEEAKS DOWN CONSTITUTIONAIi VIGOR. 179 

the brow of infancy as the poppies of eternal sleep, and enters the 
lungs and circulates as a deadly poison ; and stUl the ' shawls and 
blaniets,' sleeping and awake, are pretty generally employed to de- 
prive the objects of the most rapturous paternal solicitude, of what 
was originally breathed into the nostrils of the great archetype of the 
human race as the ' breath of life.' " 

323. Bad Air undermines the Vital Powers, — And yet the fatal effects 
of mephitic air are by no means confined to those terrible maladies. 
Cholera, Fevers, Consumption, and Infantine disease, by which the 
earth is ravaged ; by undermining the health it paves the way for all 
kinds of disorders. The human system is armed with a wonderful 
protective or conservative power, by which it is able to resist the in- 
vasion of morbific agencies. Indeed, this power of resisting disease is 
perhaps a more correct measure of the z-eal vigor of the body than its 
outward appearance of health. Individuals may often continue for 
years to breathe a most unwholesome atmosphere without apparent 
ill-effects ; and when at last they yield, and are prostrated, or carried 
off by some sudden disease, the result is attributed to the more ob- 
vious cause, the long course of preparation for it by subtle and insidi- 
ous poisoning being entirely overlooked. The mass of mankind refuse 
to recognize the action of silent, unseen causes. Our youth in the 
morning of their days, and men in the meridian of their strength, 
pass abruptly away, and we wiU be satisfied with no solution of the 
problem w^hich refers the mournful result to reprehensible human 
agency.* " The action of contaminated confined air has been shown 
to be the most potent and insidious of mortiferous agencies. Any ad- 
dition to the natural atmosphere that we breathe must be a deterio- 
ration, and absolutely noxious in a greater or less degree ; and healtli 

* " It is evident that the depressing effects of foul air are not confined to those cases In 
which the immetliate results of its poison are seen. Because it requires a given quan- 
tity of carbonic acid in the air to exhibit decided effects, it does not follow that a much 
lower proportion does not seriously impair the vital energies, and especially the power 
of resisting disease. We are firmly convinced that many a case of scarlet fever or of 
measles proves fatal on account of an unperceived depression of the little sufferer's 
strength by previous continued exposure to an atmosphere tainted with carbonic acid 
and other exhalations from his own lungs. We know that all diseases of low grade, such 
as typhoid and typhus fever, prevail to a very great extent in ill ventilated houses ; we 
know that an epidemic inflammation of the eyes has been frightfully prevalent in the 
Irish work-houses, and that it has been traced to imperfect ventilation, the eye-disease 
being merely the index of the general depression of the vital powers; we know, too, 
that in one of the Trans- Atlantic Hospitals, the mortality went down from forty in a 
thousand to nine, upon the adoption of a proper system of ventilation, and tliat it rose 
again to 24 on the subsequent abandonmont of that system. These are only illustra- 
tions ; hosts of similar facts could be cited from the records of medical science," 



180 MOKBID AND FATAL EFFECTS OF IMTUEE AIK. 

would immediately sufter, did not some vital conservative princii)lo 
accommodate our functions to circumstances and situation. But this 
Beems to get weaker from exertion. The more we draw on it, the less 
balance it leaves in our favor. The vital power, which in a more 
natural state would carry the body to seventy or eighty years, is pre- 
maturely exhausted, and like the gnomon shadow, whose motion no 
eye can perceive, but whose arrival at a certain point in a definite time 
is inevitable, the latent malaria, which year after year seems to inflict 
no perceptible injury, is yet hurrying the bulk of mankind, with un- 
deviating, silent, accelerating rapidity, to an unripe grave. It should 
never be overlooked, that by breatliing pent-up eifete air, all the ad- 
vantages of an abundance of fuel, and every blessing of a genial sky 
are utterly thrown away, and though the habitation were on the hill- 
top, fanned by the sweetest breezes of heaven, it would become the 
focus of contagious and loathsome disease, and of death in its most 
appalling aspect. On the other hand, even in the confined quarters oi 
a crowded city, rife in malaria, and where pestilence is striking whole 
families and classes, ventilation and warmth, with cleanliness, theii 
usual attendant, like the sprinklings on the lintels and door-posts o« 
the Hebrew dwellings, stand as a sign for the destroying angel, as he 
passes over, to stay his hand, for in the Avarm, fresh-aired chamber 
none may be smitten." — (Beenan.) 

324. Morbid Mental Effects of Bad Air. — Dr. Robertson remarks" 
" The health, the mental and bodily functions, the spirit, temper, dis- 
position, the correctness of the judgment and brilliancy of the imagin- 
ation depend directly upon pure air." This is strongly put, but it is not 
an overstatement. As the iuilowing stream of air is the imminent and 
instant condition of physical life, so it is the immediate material agent 
charged with the exalted function of establishing and maintaining the 
connection of mind and body. It is air acting definitely and quanti- 
tively through the bodily mechanism, that sustains the order and ac- 
tivity of the mind's faculties. Mind is thus physiologically condi- 
tioned, and one of the mighty tasks to which science must gird itself in 
the future is to work out the analysis of these conditions. Mr. Paget, 
the eminent English physiologist, remarks : " The health of the mind, 
so far as it is within our own control, is subject to the same laws as is 
the health of the body. For the brain, the organ of the mind, grows, 
and is maintained according to the same methods of nutrition as every 
other part of the body ; it is supplied by the same blood, and through 
the blood, like any other part, may bo aflected for good or ill by the 
various physical influences to which it is exposed. But I will not 



MENTAL DISTURBANCE AND DEPKESSION. 183 

dwell on this more than to assert, as safely deducible from physiology, 
that no scheme of instruction or of legislation can avail for the im- 
provement of the human mind, which does not provide with equal 
care for the well-being of the human body. Deprive men of fresh air 
and pure water, of the light of heaven, and of sufficient food and rest, 
and as surely as their bodies Avill become dwarfed, and pallid, and dis- 
eased, so surely will their minds degenerate in intellectual and moral 
power." The immediate effect of breathing impure air is to cloud the 
mind's clearness, to dull its sharpness, and depress its energy. All the 
mental movements are clogged, each faculty suffering restraint and 
perversion. The wings of the imagination are clipped, reason loses its 
keenness of penetration, and the judgment its acuteness of discernment 
and perspicacity. When we breathe bad air, the impressibility of the 
mind is diminished ; if we undertake to study, we can neither under- 
stand so clearly, nor remember so well as if the air were pure. So- 
cially we become less interesting, the spirits fall, conversation flags, 
dulness supervenes, we get impatient and irritable, and there is too 
often a resort in these circumstances to artificial exhilarants, and stim- 
ulants to afford relief, which would be better secured by freshness and 
purity of the atmosphere. 

VI.— RATE OF CONTAMINATION WITHIN DOORS. 

325. Oxygen irithdrawn by Respiration. — Any scheme for the removal 
of foul air from an apartment, and the introduction of fresh air in its 
place, involves the previous iuquiry, how rapidly ought this change to 
be made ? Our next question, then, is at what rate does the air in 
dwellings become contaminated ? The amount of air taken into the 
system by different ii.dividuals, varies greatly according to age, capa- 
city of lungs, rate of exercise, and many other circumstances. Hence 
there is much discordance in the results of inquiries made by different 
physiologists. The disagreement is also much owing to the difficulties 
attending this kind of experimenting. If we take as the basis of our 
calculation Coathupe's estimate, the lowest that we can find, we shall 
assume as an average, that there are 20 respirations in a minute, and 
at each respiration, 16 cubic inches of air pass in and out of the lungs. 
This is equal to 320 cubic inches per minute, 19,200 per hour, 460,800 
cubic inches or 2G6| cubic feet per day of 24 hours. Vierordt makes the 
quantity 306| cubic feet, Sohakling 361 cubic feet ; and Valentin as 
high as 398-2 cubic feet per day. As J of the air is oxygen, there will bo 
♦bur cubic inches of this gas taken into the lungs at each iuspiratioii. Of 



182 RATE OP CONTAMIXATION WITHIN DOORS. 

this quantity, very nearly one half is absorbed and enters the blood. 
We may safely assume that 35 i)er cent, of the oxygen is thus absorbed 
at each breath, or 7 per cent, of the entire air. The quantity of oxygen 
consumed will be 22 to 24 cubic inches per minute, 13M cubic inches or 
8-4ths of a cubic foot per hour, and 18-6 cubic feet per day. A person, 
therefore, robs of all its oxygen nearly foiur cubic feet of air per hour, 
and diminishes its natural quantity 5 per cent, in 80 cubic feet per 
hour, or Ig^ cubic feet per minute. 

326. Proportion of Carbonic Acid exhaled by Respiration. — When carbon 
is completely bui-ned in pure oxygen, the carbonic acid gas produced 
occupies exactly the space that the oxygen did before burning. If all 
the oxygen absorbed by respiration was converted into carbonic acid 
in the system, the volume of this compound gas restored to the air 
would be exactly equivalent to the oxygen withdrawn. But a portion 
of oxygen unites with hydrogen and sulphur, forming water and sul- 
phuric acid, while a small part of the carbonic acid generated within 
the body escapes into the air through the pores of the skin. The con- 
sequence is, that the bulk or volume of carbonic acid expelled from 
the lungs is not quite equal to that of the oxygen absorbed. Assuming 
the quantity of carbonic acid in the expired au- to be 5 per cent., it 
will be one hundred times greater than the natural amount in the at- 
mosphere (280). A person, therefore, by breathing adds 1 per cent, 
of carbonic acid to 55^ cubic feet of air in an hour, or would vitiate 
to this extent nearly one cubic foot in a minute. 

327. Oxygen withdrawn by Combustion. — The amount of combustion 
varies so widely with the kind of fuel used, the mode of burning it, 
the quantity of heat required, and other circumstances, that we can 
approach nothing like an average estimate of its influence upon the 
air in a given time. It is known with certainty how much oxygen 
given weights of the different fuels require for combustion, but the 
amount withdrawn from the air of a room depends entirely upon the 
rapidity with which it is consumed. A pound of mineral coal requires 
the oxj'gen of 120 cubic feet of air to burn it (90). If five pounds 
are consumed in an hour, at least GOO cubic feet of air must be re- 
moved from the room. Combustion of fuel, however, does not, like 
respiration, decompose the air, separating the life-sustaining element, 
and leaving the residue in the apartment. If properly conducted, it 
removes the air from the room unchanged, and having decomposed it 
in the fire, dismisses the contaminated product through the flue. Very 
ollen, however, when fires get low and draughts feeble, there is a re- 
fluenco of foul gases into the apartment (121). 



BY LIGHTING AND LOaS OF MOISTTTEE. 183 

328. Air yitiated by Illnminating Processes. — The case is different when 
combustion is employed for illuminating purposes, as in the burning 
of candles, oil, and gas ; these, like the body in respiration, alter the 
air within the room. A candle (six to the pound) will consume one- 
third of the oxygen fi'ora 10 cubic feet of air per hour, while oil 
lamps with large burners will change in the same way 70 feet per hour. 
As the degree of change in the air corresponds with the amount of 
light evolved, it is plain that gas-illumination alters the air most 
rapidly. A cubic foot of coal-gas consumes from 2 to 2\ cubic feet of 
oxygen, and produces 1 to 2 cubic feet of carbonic acid. Thus every 
cubic foot of gas burned imparts to the atmosphere 1 cubic foot of 
carbonic acid, and charges 100 cubic feet with 1 per cent, of it, making 
it unfit to breathe. A burner which consumes 4 cubic feet of gas 
per hour, spoils the breathing qualities of 400 cubic feet of air in 
tlaat time (224). 

329. Inflnence of Moisture upon tbe quantity of Air required. — It has 
been noticed that air which is either very dry, or very moist and 
damp, is disagreeable and unwholesome. It should not contain so 
little moisture as to dry and stimulate the skin ; nor so much that it 
Avill not readily receive the insensible perspiration which constantly 
flows to the surface. The amount of watery vapor emitted from the 
body has been stated at from 20 to 40 ounces per day. Estimates 
upon this point vary. If one of each sex be taken, the mean exhala- 
tion will be about 23 grains per minute. Now let us suppose the air 
of a room to be at 70°, and that it has to be cooled 20° before it 
begins to deposit moisture, that is, its dew-point is at 50°. The cubic 
foot of air at 50° contains 4*5 grains of moisture, and at 70° it will 
hold 8'4 grains, so that it is capable of dissolving 3-9, or nearly 4 grs. 
of water. Of air in this state, it will require about 6 cubic feet per 
minute to dissolve and remove the insensible perspiration from the 
skin. If the dew-point be lower, the air will take up more water, and 
less of it will be required to evaporate the moisture of the body. 
But if the dew-point be higher, the air will receive less moisture, and 
the system will require a larger supply. If the dew-point is at 60° 
and the temperature of the air at 70°, a cubic foot of it will become 
saturated by the addition of 2*17 grains, so that 10 feet per minute 
would hardly carry off the cutaneous exhalation. To be pleasant, air 
must not be deficient in moisture ; if it be nearly saturated, it can im- 
bibe but little, and consequently much of it must be brought in con- 
tact with the system; and this necessarily involves large provision for 
•jhauge of air. 



184 KATE OF CONTAMINATION WITHIN DOOES. , 

330. Air vitiated by one person in a minntc. — These sources of impuritj 
are capable of measurement in their rate of effect, but there are other 
influences so irregular in action that the results they produce cannot 
be estimated. The whole quantity of air tainted by emanations from 
the person, and -which requires removal, is variously stated by different 
authorities at from S^ to 10 cubic feet per minute. "We are of opinion, 
that for the restoration of its lost oxygen, the removal of carbonic 
acid, insensible perspiration, and the peculiar effluvia of the living 
body, there are required, at the lowest estimate, 4 cubic feet of air 
in a minute, or 240 per hour. But this may be much too low. 
It is evident that the nearer the air breathed within doors, approaches 
in purity and freshness to the free and open atmosphere, the better 
will it conduce to health, strength, and length of life. As far as pos- 
sible we ought not to limit ourselves to that supply which the consti- 
tution can bear or tolerate, but to that amount which will sustain the 
highest state of health for the longest time. And yet, as Dr. Reid 
remarks, the question of the amount of air to be supplied may be con- 
sidered in some respects in an economical point of view, in the same 
.manner as the table any one can afford to sustain, the house in which 
he may dwell, or the clothing he may put on. Although i)ure air is 
the most abundant of all things, yet in our plans of living it is by no 
means free of cost (363). 

331. Inflnence of size of Apartments. — The smaller an occupied room, 
the sooner, of course, will the stock of pure air contained in it be ex- 
hausted and replaced by foul air. Three persons sitting in a tight 
room 8 feet high, and 12 by 14 square, will vitiate all its air in two 
hours. If they use lights, the air will be spoiled much quicker. 
Twelve persoas sitting in a parlor 16 by 20 and 9 feet high, Avill make 
its air unbreathable withoiat the assistance of either fire or lights in a 
single hour. Two persons sleeping in a close bedroom 10 feet square 
by 8 high, will render all its air unfit for respiration in less than two 
hours. In actual practice, the cases are not quite so bad as this, foi 
with the utmost perfection of carpentry there wiU be cracks for the 
passage of air, though perhaps in small quantities ; and the opening 
and closing of doors cause intermixture and currents, and this some- 
what delays the result. Where the rooms are capacious, the reservoirs 
of air are more slowly contaminated, and if no means are taken to 
remove the foul air and introduce that which is pure, large-sized rooms 
are of the utmost importance. But no apartments of ordinary or prac- 
ticable dimensions will enclose sufficient air for the agreeable and whole- 
some use of their occupants. Tliis must be attained in another way. 



MOTIVE POWER IN VENTILATION. 185 

832. Inflnencc of Plants npoa the Air of Rooms. — The general action 
of plants upon the air is antagonist to that of animals. In the day- 
time, under the influence of light, they absorb carbonic acid from the 
atmosphere by their leaves, decompose it, and return pure oxygen to 
the air, thus tending by a double action to purify it. The rate at 
which these changes occur corresponds with the activity of growth. 
The plant, however, derives a portion of its carbonic acid from the 
soil, especially if it be rich, in decomposing organic matter, like the 
garden mould of flower-pots. Compared with the ordinary rate of 
contamination in occupied apartments, the purifying efliect of the few 
green plants usually kept, is but small. In the absence of light, the 
peculiar actions of the leaves are suspended, nay, reversed; they 
now rather absorb oxygen, and give off carbonic acid, like ourselves. 
Hence, in sleeping-rooms, their tendency would be to impurity of the 
air, though the action is probably very slight. As respects moisture 
plants are also like animals, constantly exhaling it through the pores 
of their leaves. According to Hale's experiment, a sunflower weigh- 
ing 3 lbs. exhaled from its leaves 30 ounces of water in a day. Plants 
may therefore be a useful means of supplying dry air with the requisite 
humidity. 

VII.— AIR IN MOTION— CURRENTS— DRAUGHTS. 

333. Two methods of purifying the Air. — Pure air may be secured iu 
two ways : first and most perfectly by the removal of the vitiated at- 
mosphere of the apartment, and its replacement by fresh air from out 
of doors. This is the mechanical method, and is known as venti- 
lation^ — a term derived from the Latin word signifying wind. The 
air may also be more or less perfectly cleansed by means of substances 
which absorb, decompose and destroy its noxious ingredients. This 
is the chemical method. It is useful only under certain circumstances, 
and is not applicable in common cases (802). 

334. Motive Power employed.— As ventilation consists in the move- 
ment of masses of air, it implies some kind of moving force. On a 
large scale, as for public buildings, revolving fans, pumps, bellows, «&c., 
driven by steam-engines or water-power, have been used to impart 
movement to air. But these contrivances are impracticable for 
dwellings. Wind power is often used as an aid in ventilation, but its 
unsteadiness prevents us from depending upon it. The force gener- 
ally resorted to in private residences to secure exchange of air 
is heat. 



186 



AIK IN MOTION — CURRENTS — DRAUGHTS. 




835. Cnrrents of Air in Close Apartments. — Changes of temperature 
externally give rise to unceasing commotions in the air — breezes, 
winds, and hurricanes. The same thing occurs within doors ; any 
portion of air heated becomes lighter and causes an ascending current ; 

any portion cooled becomes denser 
and causes a descending current. 
If a candle be lit in the middle 
of a room (Fig. 72) where the 
doors, windows and flues are 
closed, and the air is motionless, 
a set of currents wiU rise in the 
centre of the room, spread out 
near the AvaU, to its sides, then 
descend and return along the floor 
to the centre again. The arrows 
in the diagram show the direction 
of the currents in a section of the 
apartment. Tig. 73 shows the 
direction of the currents along the floor, that is, on a pla?},, as it 
is termed. If the arrows (Fig. 73) were reversed, they would show 
the course of the currents at the top of the room. If a lump of ice 
be substituted for the candle, currents are again produced, but they 
are exactly reversed in direction (352). The air descends from the 

cold ice, and the currents on the 
floor run outwards. In each of tliese 
cases, the currents above and below 
are opposite. AU local disturbances 
of temperature tend to produce simi- 
lar effects, although the currents are 
commonly much interrupted by dis- 
turbing forces. Of course several 
lights would occasion several cur- 
rents, which would mutually inter- 
fere with each other. A stove in 
the centre of the room produces just 
such a movement of air as we have 
seen established by the candle ; but 
if placed at one side, the hot-air ascends on that side and descends on 
the opposite. 

3&6. Niitnral Ventilation of the Person. — The warmth of the human 
body imparts itself to the layer of surrounding air, expands it, and 



Fig. T8. 




DOWNWARD CURRENTS IN WINTER FROM A\'INDOWS. 187 



Fia 74. 



causes a rising current (107). When the temperature of the room is 
65°, the body is 33° warmer, while 4° added to the circumjacent air 
will cause it to ascend and escape above the head. The simple 
presence of an individual in a room is therefore sufficient to throw 
the air into movement and cause currents. The body thus acts pre- 
cisely in the same way as a stove, and the presence of persons dis- 
tributed through a room will add much complexity to the movements 
of the air, and to a small extent counteract the stove-currents. 

337. Windows, though tight, produce Currents. — Windows, in cold 
weather, though entirely tight, so that no air passes their crevices, are 
always sources of descending currents of air, with a corresponding 
ascending movement (Fig. 74). AVhen between the internal warm air 
and the external cold air there is "only one thin film of window-glass, 
the heat escapes through it so fast that the air within is rapidly 
cooled, condensed, and becomes heavier, so that a sheet of it is con- 
stantly falling to the floor. This cascade 
of cold air is frequently so sensible in 
winter that persons are apt to suppose 
it comes from some opening about the 
window. These Avinter window currents 
are often most injurious. If there be 
draughts through the room, produced by 
a fire or any other cause, they throw the 
window current out of its direction more 
or less to one side, so as frequently to 
fall upon persons who suppose them- 
selves to be safely away from any such 
source of discomfort. Large windows 
in public rooms, in winter, should on 
this account be carefully avoided, as the 
cataract of cold air which they pour down upon the body is a fre- 
quent cause of rheumatism, colds, and inflammations. Such sheets of 
air often fall with mischievous effect upon sleepers, where beds are 
placed near windows. It may be remarked that in summer these 
currents are reversed; the heat, passing from without through the 
window glass, rarefies the air in contact with it, which rises so that the 
current passes in a contrary direction (289). 

338. The Air of rooms arranged in strata. — But the effect of currents 
is not to cause a perfect intermixture with uniformity in the condition 
ot the air throughout the room. Indeed, the very cause that gives 
rise to them is the tendency of cold air to fall into the lower place, 







^ 


-^^ 


^^- , 


..-^-""C^:*?^^ 


' --^ " 


~'- 


-S^ 






1 






\ 




'l 


i 
1 










fr 


'f 










J 


i 


.^ 


— 




J^^^^ 


b<^ 






-'■^^ ^--^^s. 


->^ - 


^^^,^^ 


^^^ "^ -*- 


-^ 



Currents produced in winter by 
single windows. 



li 



AIR IN MOTION — CUKRJSNTS — DEAUGHTS. 



while it presses upward that which is warm and lighter. Hence, not- 
withstanding its constant motion, the air is in fact arranged in layers 
or strata, according to its temperature, the hotter air collecting near 
the ceiling, and the layers decreasing in temperature downwards as 
was previously stated (125). The difference of these temperatures is 
sometimes so considerable that flies will continue to liv.e in one stratum 
which would perish in another. Now the Avarm and rarefied air which 
rises to the upper part of the room contains also the impure air which 
has been generated within it. The breath which escapes from the 
lungs, 20° or 30° warmer than the surrounding air, slowly rises above 
the head, while ascending currents from the body carry upward all 
its exhalations (334). So also the heated poisonous products of illu- 
mination mount rapidly to the ceiling. The effect of currents is, to a 
certain extent, to diffuse the foul gases throughout the apartment, but 
chemical tests show the same stratification of impurities that the 
thermometer indicated in regard to heat, the best air being below and 
the worst above. In a room having a fireplace, the cold air may enter at 
the top and bottom of a window, fall towards the floor and move 
along near it to the flue, where it is discharged. In its progress, it 
may even blow strongly upon a bed made on the floor, while all the 
air above, enveloping a bedstead of ordinary height, remains loaded 
with carbonic acid and aqueous vapor. In all ordinary rooms the 
floor is swept by draughts of cold air, and is unfit for a sleeping place, 
especially if the apartments have open fireplaces. 

839. Simple openings do not produce Cnrrcnts. — If an apartment be 
opened to the external air, various movements are liable to occur, or 

there will be 
DO motion at 
all, according 
to circum- 
stances. It 
by no means 
follows that 
because a 
communica- 
tion has been 
opened be- 
tween a room 

and the outer air, therefore currents will set in and an active inter- 
change take place. Air will not leap out of a bottle because we ex- 
tract the cork, nor out of a window simply because we open it. Cur* 



Fio. T6. 



Fio. 76. 



50' 



-60" 



-a^ 



60" 



Conditions in which opeulngs in rooms do not produce 
exchange of air. 



INTEKOIIANGES THROUGH "WINDOWS AND DOORS. 



189 



Fio. 73. 



rents cannot be produced unless their cames are brought into action. 
If a room be opened below, and the temperature within be higher 
than that without, as represented in Fig. 75, the outer, heavier air, 
pressing harder than that within, will confine it, no movement will 
take place, and the strata will retain their relative positions undis- 
turbed, as in the figure ; or, if the room be opened above, and the 
external air be warmer than the internal (Fig. 7G), the lighter air with- 
out cannot press down to displace the inner, heavier air, which re- 
mains without movement or disturbance of its arrangement. 

340. Currents between rooms and external Air. — If there be an open- 
ing at the lower part of a room, and the external air be warmer 
than that within, interchange takes place, the outward air displacing 
that within by currents running as the arrows show (Fig. 77), the 
heavier air within falling or flowing out. If the opening be above, 
and it be 
Avarmer in- 
side than 
out, the light 
air inside 
will escape 
upward, and 
thecold,hoa- 
vy air Avith- 
out flows in, 
as shown in 
Fig. 78. If 

there be but a single opening to a room, although all other condi- 
tions are favorable for a change, yet the counter currents meeting in 
the passage conflict, and to a certain extent obstruct each other. 
There should, therefore, be separate openings for currents of ingress 
and egress. 

341. Friction of eonnter-cnrrents of Air. — The importance of having 
two independent openings to an apartment, if we desire to secure a 
change of air, is shown by the following simple experiment : Take a bot- 
tle with the bottom removed, or a lamp chimney (Fig 79), place under it 
a short piece of burning candle in a shallow dish of water, so that no 
air can get in from below ; now, although the stopper be removed so 
that the inside of the bottle has direct communication with the outer 
air, the candle will go out. Although there is a tendency of the 
burnt air to escape and of the fresh air to rush in, yet they cannot 
pass each other at the open mouth ; the currents conflict and the 




Conditions in which openingg in rooms produce exchange of air. 



190 



AIR IN MOTION — CUKEENTS — DEAUGUTS. 




Effect of separating 
the air currents. 



Fig. 



exchange does not take place. Yet, if a slip of paper be inserted in 
the mouth of the bottle or lamp-glass, as seen in Fig. 79, thus dividing 
it into two distinct apertures, the lit candle will con- 
tinue to burn. The foul air will pass out on one side 
of the pasteboard and the pure air enter on the 
other, as may be shown by the smoke from the snuff 
of a candle held near ; it will be drawn in on one side 
and carried up on the other. The purity of the air 
within is thus secured. When the opening, how- 
ever, is sufficiently large, the currents pass without 
difficulty, as is easily illustrated. If the door of a 
warm apartment be opened, and a caudle placed 
near it on the floor, the flame will be blown in- 
Avards ; if it be raised nearly to the top of the door 
it will be blown outward, as illustrated in Fig. 80. The warm air 
flows out at the higher openings. If the air of the room be warmer 

than that without, it enters by all the 
crevices near the bottom, and escapes 
. by those near the top, and the reverse 
if it be colder. 

342. Currents throngh Windows. — 
Draughts through windows and doors 
are often not eftectual in removing all 
the air of rooms. In the case just 
r . instanced (Fig. 80), of the open door, 
/. Jhe cold air below enters and expels 
^an equal portion of the warmer air, 
' but only that Avill flow out which lies 

~r, \ . . ., ,' below the level of the door-top. The 

Counter-currents in the aoorway. "^'^^ ""^ '^ ^ 

mass of air above this level will not 
be displaced. If, however, the temperature of the room were at 60°, 
and that of the outer air at 70°, an open door would evacuate the 
room entirely of its airy contents ; the colder air in the room tending 
to full would pour out at the bottom, and the warm air enter at the 
top to take its place. If a window be situated in the upper pai-t of 
the room and opened, its action is difterent, and in a manner opposite 
to that of the door. When the air is cold without and warm within, 
and the Avindow opened above and below, the apartment is emptied 
and refilled as in Fig. 81. If the external air is warm and that Avithin 
cool, all above the window sill is removed (Fig. 82), but the cold air 
beloAV that level continues undisturbed. By thus understanding tho 




INTERCHANGES TUEOUGH 'WINDOWS AND DOOKS. 



191 



Fig. 81. 




Condition in which the air escapes 
above. 



conditions of inflow and outflow, we are enabled to regulate windows 
having both sashes movable, and which are often valuable for venti- 
lating private rooms. Although the interference of other causes is 
Uable to modify, and perhaps often 
confuse and divert these movements, 
yet they are quite sufficient to show 
that the motion and rest of air are 
controlled by laws as definite and reg- 
ular as those which govern the mo- 
tion, and rest of water. Though infi- 
nitely more light, mobile, and easily 
agitated, yet it is never thrown into 
commotion except by adequate and ap- 
preciable causes. 

343. How cnrreats of Air affect the Sys- 
tem. — The sensations produced upon 
the body by gently-moving currents of 
air in proper conditions of temperature and moisture are extremely 
agreeable, but in many cases streams of air directed against the per- 
son become most injurious. Air at low temperatures of course has a 
cooling effect. "We lose no more heat by radiation in moving air than 
in still air, but by conduction we lose heat 
in proportion to the velocity of the cur- 
rent or the number of particles which 
come in contact with the body. The cur- 
rent also drives the cold air through the 
clothing, displacing the warm air which 
was entangled in its pores. Increased 
evapoi'ation, proportional to the dryness 
and speed of the air, is also a further 
source of cold. If the whole surface of 
the body is exposed to the current, the 
effect will be simply a general cooling 
without any necessarily injurious effects. 
But if the draught fiill only upon some 
one part of the body, it is liable to produce serious mischief, disturb- 
ing the circulation and producing febrile movements, which may be 
directed to the part exposed to the draught or even to remote organs, 
in either case often laying the foundation for serious and fatal disease. 
This point should be particularly considered in introducing air in suna- 
mer which has been artificially cooled (352) ; its diffusion should be 



Fig. 




Conditions in -which the air 
escapes below. 



192 ARRANGEMENTS FOR VENTILATION. 

very extensive and its velocity hardly perceptible. Of course we can- 
not have ventilation without movement of air, but the motion should 
be so moderated that we are not aware of it, and is always to be con- 
sidered in connection with the two important conditions of tempera- 
ture and moisture. We have made several trials to determine the ve-; 
locity which, as a general rule, with a proper regard to other condi- 
tions, will not be found unpleasant, and give as the result about two 
feet per second. It is evidently no greater than that with which we 
sliould pass through still air when walking with the same velocity. 
(Wyman.) Yet it is important that we be exposed to currents. Few 
things are more favorable to taking cold than the confined and stag- 
nant air of unventilated apartments. Just in proportion as we habit- 
uate ourselves to such stiU, stagnant air, do we become sensitive to at- 
mospheric changes, against which it is impossible perfectly to protect 
ourselves on going out. The effect of a free internal circulation of air 
in our rooms is therefore most salutary; the more we are accustomed 
to it, the safer we are in the vicissitudes of changing weather, 

VIII.— ARRANGEMENTS FOR VENTILATION. 

344, The open FireplacCt — The mechanical expedients for securing 
exchange of air in dwellings are numerous, but they are chiefly con- 
nected with arrangements for heating. Wherever there is active com 
bustion in stove or fireplace, there must be a stream of air passing 
out of the room through the chimney. If the room be absolutely 
tight, so that no air can enter it, none will ascend, and if the fire be 
kindled the chinmey will smoke. A draught through ' a chimney im- 
plies openings somewhere for air to enter the room, and thus there is 
some ventilation as a matter of necessity. In noticing the heating ef- 
fect of the fireplace, we saw that the open space above the fire con- 
veys away a large amount of warmed air from the room, which took 
no part in the combustion and wasted much heat. But this fault was 
an advantage in respect of ventilation. The magnitude of the open 
space above the fire represents the ventilating capacity of the chim- 
ney. But it is from the air below the level of the mantel — the purest 
in the apartment — that the fireplace is supplied. Only so much of 
the foul imprisoned air above as gradually cools and descends, be- 
ing swept into the chimney. When the weather is quite cold, the 
briskness of the fire that is demanded, occasions a powerful draught 
and produces annoying currents. So powerful were these draughts in 
old times, that they were compelled to use a settle, a long bench with 



ACTION OF FIREPLACIiS AND STOVES. 193 

a high wooden back, to protect the body from currents and retain the 
radiant heat in order to keep warm. " It would be well for those who 
question the importance of ventilation, because our forefathers lived 
to a good old age without even understanding the meaning of the 
word, to remember their fireplaces, the kind of dwellings they occu- 
pied, and the quantity of air which must have passed through their 
houses." It cannot be doubted that the changes which have of late 
years been effected in the structure of the fireplace to secure the 
greater economy of fuel — the contraction of its dimensions and the 
lowering of the chimney-piece, by diminishing the amount of air ihat 
was forced through the room to fill the capacious chimney, and by 
bringing the foul-air space down more completely within the xone of 
respiration — have been altogether unfavorable ; although, even in their 
newer construction, open fires may be considered as affording a toler- 
able amount of ventilation. Fresh air is well secured by the double 
fireplace, which warms and introduces into the room a steady stream 
of air from without. (111.) 

345. Ventilation by Stoves. — ^As respects the condition of the air, the 
exchange of even the low and contracted fireplace for the close and 
stifling stove, has been eminently promotive of discomfort and disease. 
Stoves afford the least ventilation of all our means of heating. They 
take little more air than just suflicient to consume the fuel, and that 
is withdrawn from the purer portion near the floor. In most cases of 
the use of stoves, no provision whatever is made for the removal of 
bad air. They may be made subservient to ventilation in several 
ways; flrst, by allowing^air to pass through tubes in the body of the 
stove ; second, by admitting it between the stove and an external 
casing ; and third, by simply allowing it to strike upon the external 
surface of the stove. In either case the entering air will be warmed, 
rise toward the ceiling, and afterward gradually descend as the air 
below is drawn off, producing a downward ventilation through the 
whole apartment. Mr. Euttan, of Coburg, 0. W., has devised a plan 
of heating and ventilating, strongly recommended by those who have 
used it, although we have had no opportunity of seeing its operation. 
He locates his 'air- warmer' in the hall, or where required, brings in 
the air from below, heats and transmits it through the building. For 
the best working of his arrangement it is important that tlie house be 
built with reference to it ; indeed, he insists that the general failure to 
ventilate is because the architects fail to provide the necessary lungs 
in the original construction of dwellings (3G2). 

346. Ventilation by Hot-Air Arrangements. — Sources of warmth be- 

9 



194 AEEANGEMENTS FOR VENTILATION. 

come the most effective uieans of ventilation when air itself is made 
the vehicle for conveying heat into the room, as in the use of hot« 
water apparatus, furnaces, &c. The hot current enters through a 
register, or guarded opening, and streams up at once to the ceiling ; 
and by diffusion through the apartment, displaces the air already 
present, which must find escape somewhere, and thus the renewal of 
the breathing medium is constantly secured. Apartments warmed in 
this manner require a chimney or other place Ly which air may escape. 
The fireplace answers perfectly ; but under the impression that rooms 
heated by air-currents require no channel of escape, houses have been 
constructed with no flues at all. The air ought to be projected into 
the room horizontally or at different points, so .as to be well diffused 
(125). It should always be derived from perfectly pure sources, and 
never used a second time. But the chief difficulty and danger, as 
before noticed, is to be found in that condition of the air itself, which 
results from its being suddenly heated (305). 

347. The supply of Hloistnre. — The provision for supplying moisture 
by evaporation is rarely any thing like adequate, a supply of 35 cubio 
feet of air per minute introduced at the temperature of freezing and 
heated to 90^, is capable of taking up an ounce of water per minute, 
or four pounds in an hour. Dr. Eeid states, that in ventilating the 
English House of Commons, when it was crowded, he often exposed 
the air furnished to 5,000 feet of evaporating surface, to impart the 
necessary moisture, and stilsequently made the air flow through jets 
of water. The artificial supply of moisture to air in the exact quan- 
tity required, involves grave difficulties. The common method of 
supplying humidity by simmering water in an open vessel, is glaringly 
insufficient. A pan of water is placed in a furnace,* but of the torrent 
of air that rushes through, how little is brought into contact with the 
water. We place a vessel upon a stove with a few square inches of 
water-surfoce, and foncy all is right, but the air may still be parching 
dry. Where air in cold weather is introduced, suddenly rarefied by 
heat, and actively changing, we have little conception of the amount 
of moisture which must be artificially added to give to it soft and 
balmy qualities. The best thing to be done of course is, to obtain the 
largest possible evaporating surface. To accomplish this, a piece of 
linen or cotton cloth dipped in a vessel of water, may be hung in folds 
from any convenient framework or support. The cloth, by sponging 

* Walker's furnace, manufactured by S. B. James, No. 77 White strcov, New York, 
cas large provision for evaporation, which the proprietors offer to increase to any 
extent that indiviiluals may demand. 



HEATING CONTRIVANCES THAT BEST EFFECT IT. 195 

up the water is always wet, and gives out its moisture to the air. If 
previously dipped into a solution of potash, which is very absorbent 
of water, it continues more perfectly wet. If it be unsiglitly, the sus- 
pended cloth may be concealed from view by any graceful screen, as 
by a tower-shaped cover of porcelain, open above and below to admit 
the passage of air. "Where hot-air is used, it may even become neces- 
sary to mingle with it the vapor of boiling water. 

348. Best method of Warming and Ventilation. — If we would have the 
pleasantest mode of warming and ventilating a dwelling-house, with- 
out regard to trouble or expense, we should certainly combine the 
open fireplace with air-heating apparatus, which should never exceed 
in temperature 212°. The first is desirable for its pleasant light and 
radiant heat, while the second gives to the entries and chambers a 
mild atmosphere, which prevents cold draughts from open doors, and 
at the same time, through an opening in each apartment, moderately 
warms it, and likewise supplies air for the ventilation going on by the 
fireplace. The fireplace also has its influence upon the inti'oduction 
of the warmed air. The heat of the chimney establishes a current 
which draws from the air-heating apparatus a large supply of air at a 
lower temperature than would otherwise enter the apartment. We 
know of no single apparatus which warms and ventilates a dwelling- 
house in so healthy and comfortable a manner as is accomplished by 
this coml)iuation. — "Wtman. Yet it can only be had by very few ; for 
the mass of the people it is entirely out of the question from expen- 
siveness. 

349. Snpply of Air by loose Joinings, Crevices, &c. — Ilot-air con- 
trivances of any kind, although coming more into use, especially in 
cities, are by no means general. Grates and stoves are the nearly 
universal sources of heat, and the latter of these cannot be said to 
ventilate at all. No provision is made for the entrance and exit of 
air. The use of doors to rooms is for the admission of their occu- 
pants, windows are for the entrance of light, and it would certainly 
seem, both from its importance and peculiar properties, that air also 
is entitled to an entrance of its own. Yet in most cases we treat tlie 
ah- as if it had no business in our dwellings. It has to avail itself of 
the mechanics' botch-work or the chance shrinkages of time, and 
creep through any crevices and wind-chinks that there may happen 
to be, or dodge in and out at the casual opening of windows and 
doors. These cracks and loose joinings afibrd a kind of imperfect 
accidental ventilation, which, by effecting the purpose in a partial 



196 ARRANGEMENTS FOR VENTILATION. 

degree, has prevented mankind from discovering the want of any 
thing better. 

350. Four points to be secured In Ventilation. — Tliat ventilation may 
be complete, and do for us its best service, four things must be at- 
tended to. 

First. Pare air must be introduced. 

Second. The foul air must be removed. 

Third. The supply must be sufficiently copious. 

Fourth. There must be no oflfensive currents. 

Now as things usually are, none of these points are certainly se- 
cured. There is no constant and regulated supply of air, this being 
left entirely to chance. There is no provision for the exit of the 
vitiated gases. All the air that is drawn off from the apartment is 
taken from its lower and purer portion by the draughts of the stove 
and fireplace, while that which should escape stagnates above. The 
quantity furnished is therefore variable and usually stinted, while in- 
jurious draughts are notoriously common. Independent and eifective 
methods of changing the air, by which these enumerated benefits may 
be gained, are on every account desirable. 

351. Modes of introdacing pure Air from without. — In summer the 
free opening of doors and windows ensures a supply of air. It is a 
good plan to have light door-frames fitted to the outer entrances, and 
covered with wirecloth or some loose fabric, as miUinet, through 
which the air will pass readily, but in a diffused manner. In Avinter 
the air should always, if possible, be warmed before being thrown 
into the apartment. For introducing more fresh air than accidental 
fissures will admit, the readiest way is to lower the top window sash, 
although the stream of cold air which presses in and is both unpleas- 
ant and unsafe, falL^ to the floor and glides to the stove or fireplace 
without being sufficiently commingled with the general atmosphere to 
serve the purpose of ventilation. It becomes a mere feeder of the fire. 
To disperse cold currents of air fi-om above, a plate of zinc perforated 
with numerous holes is made to replace the pane of glass furthest from 
the fireplace and in the upper row of the window. Louvres made 
either of tin, zinc or glass, with horizontal openings and slats like 
Venetian blinds, are also substituted for window panes. A small tin 
wheel or whirligig, which revolves and scatters the inflowing current, 
is sometimes mounted in the window ; it is often noisy and rattling. 
In arranging openings for the entrance of air, several circumstances 
are to be borne in mind. The air should always be fresh from with- 
out and not, as is too often done where hot-air furnaces are used, 



INTRODUCTION OF AIR INTO DWELLINGS. 



19^ 



Fig. 83. 



taken from cellars or baseiueuts, or what is still worse, used over and 
over again. If there be local sources of impurity in the vicinity, 
apertures should not be placed favorably to its admission, "Where 
dust is an annoyance, or from any cause there is contamination of air 
near the ground, the supply may be brought from the top of the house. 
Oi)enings are made under the caves, or in some eligible place near the 
summit, leading to channels left in the walls, called fresh-air venti- 
ducts^ which pass down and open into the room in any convenient 
manner. The prevailing direction of the wind should also be noticed, 
as it is desirable to command its aid as far as possible ia forcing air 
into the building. Emerson's injector (Fig. 83) causes a downward 
current from whatever quarter the wind may 
blow upon it. All outer apertures should be 
guarded with valves. Air entering them and — ^S 
led along proper passages, either in tin tubes 



or air-tight wooden boxes, is admitted into 
the room at various points. There may be 
an air passage made along behind the base or 
mop-board, communicating with the room by 
innumerable minute openings, through which 
the air passes. Or the inflowing currents 
may be received through registers or made to 
I'ise through small apertures in the floor. 

352. The downward Carrent — Air once breathed must not be again 
brought within the sphere of respiration, but should it be removed 
downward or upward ? The air thrown from the lungs escapes hori- 
zontally from the mouth and downward from the nostrils ; it may 
then be swept without difficulty by the ventilating current in either 
direction. In cases where hot air is thrown into the room, it first rises 
to the ceiling, and then, as it is gradually cooled, falls, and is mainly 
drawn off by the fireplace below the plane of respiration. This is in 
effect a downward current, but it is hardly strong enough to carry the 
breath down with it. It ascends, is diluted by the upper air, and fall- 
ing again is liable to be reinhaled. A descending current of air arti- 
ficially cooled has been employed for ventilation ; in fact, rooms can 
be as effectually ventilated in summer by the aid of coolers placed 
above them, as they are in winter by the heater leloio them. Lyman's 
ventilator (Fig. 84), consists of a reservoir of ice — A^ the bottom of 
which is an open grate; J5 is a gutter to catch the water from 
the melting ice ; C is a pipe or flue, through which a stream of 
cold condensed air falls constantly, as shown by the course of 




Emerson's Injector. 



198 



ARRANGEMENTS FOR VENTILATIO^. 




the arrows; Z), a wire gauze box filloil with cliar 

coal, wliich prevents the waste of ice by radiation, 

and disinfects and purifies the descending air. The 

foi'ce of the current depends on the length of the cold 

air flue and its temperature, compared with the outer 

air. In hot weather the breeze continues quite brisk. 

This arrangement, on a small scale, has been mounted 

on secretaries, to secure a cool and refreshing air while 

writing; over beds, to cool the air while sleeping; 

and over cradles, to furnish pure air for sick children 

^ (341). 

L^ 853. The ascending Current most Natural. — "We have 

., , ,7*^ noticed that by a beautiful provision of nature, xenti- 
Lyman s cold air *' ' ' 

flue. lation of the fcrson is constantly taking place. The 

exquisite mechanism of the human system would have been created to 
little purpose if it had been left to smother in its own poison. A gentle 
and insensible current constantly rises from the body, which carries 
all that might be injurious into the higher spaces. Vitiated air would 
thus constantly escape from us if it could. But in our houses we de- 
feat the benign intentions of nature by enclosing the spaces above us, 
so that the detrimental gases accumulate in the upper half of the 
room, surrounding the head and corrupting the respiratory fountain. 
It is thus evident that if we desire to aid nature in her plans, we must 
remove or puncture the air-tight covers of our apartments, so that the 
ascent and complete escape of* foul air shall not be obstructed. 

354. Ventiducts and Ejectors. — Openings for the escape of these bad 
gases above are indispensable. Each room fifteen feet, square, for the 
accommodation of six or eight individuals, should have a flue for the 
escape of foul air, either in the chinmey or elsewhere, of at least 100 
inches area. A bedroom should have an outlet of nearly the same 
dimensions. But in practice a serious diflScidty is encountered here. 
If we make an opening out from the top of the room, either by low- 
ering the top sash of a window or by carrying up a duct through the 
roof, instead of the foul air escaping through them, a flood of cold air 
rushes in from without. Tubes or ventiducts, connecting the room 
with the top of the house, may be made to act exhaustively, and drain 
the apartment of its polluted air, wlien the wind llo7cs, by surmount- 
ing it with Emerson's Ejector (Fig. 85), and as the air is almost con- 
stantly in more or less rapid motion, this arrangement becomes very 
serviceable. 

355. Opening into the Chimney — Arnott's Valve. — But the force of 



ARNOn'S SELF-ACTING VALVE. 



199 




draugkt in the chimney is after all to be the main reliance in convey- 
ing away foul air. Its necessary actioa is that of a drawing or suck- 
ing pump, which exhausts the room of large quantities of air. As the 
velocity of smoke in a chimney with a good fire is estimated to be 
from 3 to 4 feet per second, its exhaustive power is amply sufficient 
to make it serve the secondary purpose of a ventilating flue. Ilence, 
if we make a hole into the chimney, by knock- 
ing out two or three bricks near the ceiling, the 
foul gases will rush in, and mingling with the 
ascending current will escape. Yet these ven- _ 
tilating chimney openings are liable to the se- 
rious and even fatal objection, that when from 
any cause the current in the chimney is inter- 
rupted, smoke is driven into the room. An 
ordinary register, requiring personal attendance 
to open and close it, would be of no service. To Emerson's Ejector, 
remedy this inconvenience. Dr. Aenott has contrived a self-acting sus- 
pension valve. It is so placed in the aperture, and so mounted, that a cur 
rent of air passing into the chimney opens it, while a current in the con- 
trary direction closes it. It is so delicately suspended that the slight- 
est breath of air ^jresses it back, while 
any regurgitation of the chimney current 
Bhuts it, and thus prevents the backward 
flow of smoke into the room. It is showi; 
in Fig. 86. Owing to the unsteadiness (it|| 
the currents, the valve is constantly vibrat- 
ing or trembling, and would be noisj^ but 
that it is made to strike against soft 
leather. A modification of this valve Arnott's Vaive. 

consists of a square piece of wire gauze set in the opening, with a cur- 
tain of oiled silk susf-ended behind it. The current into the chimney 
pushes back the pendant flap, while a reversed current drives it against 
the gauze, and thus closes the apertm-e against the admission of flre- 
furaes and smoke. These are easily placed m fire-boards used to close 
the fronts of chinmeys. 

356. Importanee of Arnott's Valve. — The value of this valve to the 
public can hardly be exaggerated. Mr. Teedgold expressed what 
many have felt, when he said that all the plans he had seen or read ot 
for drawing off the air from the top of a room^re objectionable, either 
from being wholly ineflicient or from causing the chimney to smoke. 
This valve first meets the dilficulty. It is cheap, easily inserted, may 



Fm. 




200 AEEAJsrGEiiE]srrs for ventilation. 

be managed with trifling care, and drains the room eflfectively vi its 
gaseous pollutions. In the thousands of stifling, stove-heated rooms, 
where palor of countenance, headache, and nervousness, bear painful 
witness to the perverted and poisoned state of the air, this simple me- 
chanical contrivance might bring happy relief. It is much used in 
England, but has not been made sufficiently known in this country. 
We have inquired for it in vain at many establishments. It is manu- 
factured by S. B. James & Co., 77 White street — price, $2 50 to $5, 
according to size. If the orifice in the chimney be deemed unsightly, 
it may be screened from view by placing a picture before it. 

357. Chimney Currents in Summer. — The air in the chimney is usually 
somewhat warmer than the external air, even when there is no fire, 
and this will occasion a slight draught, so that if there be an aperture 
in the upper part of the room into the flue, and the fireplace be 
closed, the vitiated air above wUl be removed. This exhaustive ac- 
tion of the chimney without fire, is aided by winds blowing across its 
top, which exert a slight suction influence, or tendency to form a 
vacuum within it. This effect of the wind will be much increased if 
the chimney be mounted with an ejector (354). A slight fire in afire- 
place, even when not wanted for warmth, is often desirable for ven- 
tilation. Lamps have been sometimes introduced into flues for the 
purpose of exciting currents. 

358. An additional Ventilating Flue. — If an extra flue be constructed 
adjoining the chimney, warmed by it and opening into the top of the 
room, there will be a draught through it, and it may be devoted ex- 
clusively to ventilation. It would seem that such a secondary flue 
would not be liable to refluent smoke, and might have connected 
tubes extending to remote rooms, thus effectually ventilating the 
whole building. But practically such shafts do not well succeed. 
Double outlets in the same apartment rarely work satisfactorily. The 
chimney is liable to convert the extra flue into a feeder of the fire, 
and thus, if it be of the same height as the chimney, to suck back the 
smoke into the room. " Such cases have occurred, and the ventilating 
flue has been closed in consequence. This evil can be remedied by 
providing a free supply of air for both air and smoke flues. But the 
air which enters must be warmed, or it will not be tolerated, and if it 
is too much warmed, as compared with the air of the room, it will 
rise immediately to tlie ceiling and escape through the ventilator, and, 
not mingling with the air of the room, it will greatly diminish or en- 
tirely prevent any change of air where most wanted." 

359. Ventilation of Bedrooms. — The bedroom, the jjlace where we 



SPECIAL DEMANDS OF THE BEDROOM. 201 

spend nearly half of our lives, in its general condition and manage- 
ment is the opprohrium of civilization. No place in the house should 
be more copiously supplied with air to guard us against the injurious 
agencies to which we are nightly exposed. The materials of which 
bedding is composed have a strong tendency to attract moisture from 
the air and become damp. Not only are the textile fibres highly hy- 
groscopic, or absorbent of atmospheric moisture, but tlie coldness of 
rooms in which beds are usually placed, fiivors the deposit of moisture 
when the air is charged with it* They are also saturated with bodily 
perspiration. Beds should, therefore, be often and thoroughly aired. 
Their injurious effects when damp are much more dangerous than 
those of wet clothes. As the body is at rest while we sleep, there is 
no exercise to warm the surface and throw off the ill effect, as can be 
done with damp clothes. Moreover, as the vital activity is depressed 
during the state of slumber, the system is more open to the malign in- 
fluence of cold or other causes. Many and fatal diseases, inflamma- 
tions, rheumatisms, catari'hs, asthmas, paralysis and consumption, are 
induced by a want of precaution in this particular. Yet with all these 
demands for capacious drying air-space, bedrooms are apt to he scan- 
dalously small and low, damp and unwholesome. They do not usually 
contain fireplaces to drain off the bad air, and the lack of all ventila- 
tion is made worse by the popular dread of draughts, which prevents 
the opening of windows. There is urgent necessity for the adoption 
of some means of relieving them. Opening the window 
above and below is very serviceable; lowering the upper 
sash, with an opening over the door, and currents in halls? 
also give? relief. But if the bedroom have no fireplace, it 
shoul'd be connected by tubes with the chimney flue, the 
aperture being guarded by an Arnott's valve. 

360. Ventilating Gas-barners. — As we before remarked, the 
common mismanagement of gas is a forcible illustration of 
the effect of ignorance or thoughtlessness, in often turning 
the best things to the worst account. Gaslight is cheap, 
brilliant and convenient, the very qualities we want ; and so 
we turn it on and enjoy the flood of light. But bad air and 
headache supervene, and then gas-lighting is condemned, 
though the real fault is lack of ventilation. The use of gas- 
light greatly heightens the necessity for eftective change of air ; it 
generates poison exactly in proportion to its brilliancy. Dr. Fara- 
day adopted the following successful plan to ventilate gas-burners 



202 AKRANGEMENTS FOK VENTILATION. 

He placed a metallic tube about an inch in diameter over the lamp- 
glass, dipping down into it (Fig. 87) one or two inches, and connect- 
ing by its other extremity with a flue. But this was thought to be an 
ungraceful appendage to the chandelier, and has not come into use. 
He devised another, by which the tube carrying oS the products d 
combustion, returned parallel with the supply pipe, but we have not 
seen it. There is report also of a still more elegant and successful 
English contrivance, but it cannot yet be found in this country. 

861. Ventilation of Cellars. — It was seen that cellars are fountains 
of oifensive air, which ascends through crevices in the floor, doors, 
windows, and stairways, often infecting the upper apartments with 
the noxious cellar atmosphere. If cellars are to be tolerated under 
our houses, they should be thoroughly ventilated. Perhaps the best 
plan is to extend a flue from the chimney down into the cellar, by 
which the fire-draught above shall constantly drain it. A tube or 
passage from the cellar to the top of the building, mounted with an 
ejecting cowl, answers a good purpose. Some go for abolishing cellars 
altogether.* 

362. Ventilation shonld be provided for in Building. — There can be 
little question that the whole policy of warming and ventilating 
dwellings is yet in an unsettled and transition state, although this 
affords no apology for neglecting the subject. Much is known, and a 
great deal may be done about it to promote health and preserve life. 

* " While I would condemn cellars and basements entirely, the common plan of build- 
ing, in their absence, must be condemned also. The house being built above the surface 
of the earth, a space is left between the lower floor and the ground, which is even closer 
and darker than a cellar, and which becomes, on a smaller scale, the source of noxious 
emanations. Under-floor space should bo abolished as well as cellars and basements. 
The plan that I have adopted with the most satisfactory success, to avoid all these evils, 
is the follo\ving: Let the house be built entirely above the ground ; let the lower floor 
be built upon the surface of the earth, at least as high as the surrounding soil. If filled 
up with any clean material a few inches above the surrounding earth, it would be better. 
A proper foundation beiug prepared, make your first floor by a pavement of brick, laid 
in hydraulic cement, upon the surface of the ground. Let the same be extended into 
your walls, so as to cut off the walls of your house with water-proof cement, from all 
communication with the moisture of the surrounding earth. Upon this foundation build 
according to your fancy. Tour lower floor will be perfectly dry — impenetrable to moist- 
ure and to vermin; not a single animal can get a lodgment in your lower story. By 
adopting this plan, your house will ba dry and cleanly ; the atmosphere of your ground 
floor will be fresh and pure ; you will be entirely relieved from that steady drain upon 
life, which is produced by basements and cellars, — and if you appropriate the ground- 
floor to purposes of storerooms, kitchen, &c., you will find that the diy apartments thus 
constructed are infinitely superior to the old basements and cellars. And if you place 
your sitting and sleeping rooms on the second and third floors, you will be as thoroughly 
exempt from local miasma as Architecture can make you." — Dr. Buchanan. 



WHY THEY AEE NOT UNIVEESAL. 203 

Provision should be made for veutilation in the first construction of 
dwellings, as it may then be effectually and cheaply accomplished. 
The introduction of adequate arrangements, after the buildmg is 
finished, is costly and diflEicult. The necessity is absolute for including 
ventilating provisions in houses as well as those for heat. Architects 
and Builders should make them a primary and essential element of 
their structural arrangements, and design in accordance with the prin- 
ciples of ventilation as an established art. It is to be regretted that 
too many in those profession^ to which a careless public commits its 
interests in this particular, are profoundly unconscious of the just 
claims of the subject, and totally unqualified to deal with it properly. 
This is hardly a matter of surprise when we recollect how recent it is 
that science has thrown its light upon the physiological relations of 
air. It is almost within the memory of men still living that oxygen 
gas was first discovered^ and it is within twenty years that Liebeo an- 
nounced the last constant ingredient of the atmos^jhere (280). Archi- 
tecture on the contrary rose to the dignity of a regular art thousands 
of years ago, when men had little more intelligent understanding of 
the real import of the breathing process than the inferior animals. 
"We have therefore little cause for amazement when a book appears 
upon the subject of Architecture, of more than a thousand pages, and 
dispatches the whole matter of ventilation in ten lines — and that, too, 
with a sneer. Our buildings are hence commonly erected with less 
reference to healthful comfort than outside show, and ventilation is 
too much looked upon as a mere matter of tin tubes and Imocking 
out bricks, that may be attended to at any time when it may be 
thought necessary, 

363. Ventilation inTOlyes necessary loss of Heat. — The real practical 
diflBculty in ventilation is its cost. Although the atmosphere is every 
one's property, and is the cheapest of all things, yet a supply of pure 
air in dwellings is by no means free of expense. To ensure ventilation 
we must have motion of air, and to produce motion demands force, 
which is a marketable commodity. Whatever will produce available 
force has value in it. Whether it be fans and pumps driven by steam- 
engines, or upward currents set in motion by naked fire, in both cases 
there is expenditure of fuel. It is true we may use the fire that must 
be kindled to produce warmth, and thus secure the additional result 
of ventilation, apparently without additional cost. But in nx)st cases 
foul air is also warm air, and in escaping conveys away its heat, which 
is thus lost. Contrivances have been proposed, by which the outflow- 
ing warm air may be made to impart its heat to the incoming cold 



204 AEEANGE&EENTS FOR VENTILATION. 

i 

air, but they are not yet reduced to practice. Until that is done, heat 
must continue to be lost by ventilation, just in proportion to its extent. 
Hence, as was before remarked, ventilation may be classed with food 
and apparel, and it becomes a question of how much can be afforded. 
But there is this important difference, that while economy in the 
latter — a plain table and coarse clothing — are at least equally favorable 
to hea]th with more expensive styles of eating and dressing, economy 
of ventilation on the contrary, that is, any cheapening or deterioration 
of the vital medium of breathing, is injurious to health. One of the 
worst evils of scarce and expensive fuel is, that the poorer classes feel 
compelled to keep their rooms as tight as possible to prevent the 
escape of warm air and the consequent waste of heat. 



PAET FOTETH. 

ALIMENT. 



I.— SOURCE OF ALIMENTS— ORDER OP THE SUBJECT. 

364. View of the origin of Foods. — The ground thus far traversftd has 
furnished abundant illustration of the close alliance between man and 
the material universe, and of his subjection to physical influences ; l)at 
we are now to see that he is composed of exactly the same materials 
as the solid globe upon which he dwells. Eocks, corroded by the 
agencies of time and crumbled into soils, join with the ethereal ele- 
ments of the atmosphere, to furnish the substances of which the 
living body is composed. But rocks, soils, and air are not food. They 
are unorganized, lifeless matter ; and can neither nourish the body, 
nor have they the power of uniting themselves together into nutritive 
compounds. The forces which play upon terrestrial atoms, throwing 
them into movement, arranging them into vital groups, and endowing 
them with the capability of becoming parts of animal systems, are 
shot down from the heavens. The impulses of organization and 
growth are not inherent powers of our earth, residing in air and soil. 
In the plan of the universe the Sttk, a star among the stellar systems, 
is the architect of living forms, the builder of terrestrial organization, 
the grand fountain of vitality. His rays are streams of force, which, 
after travelling a hundred millions of miles through the amplitudes 
of space, take effect upon the chemical atoms of the earth's surface — 
its gases, waters, minerals, and combine them into nutritive, life-sus- 
taining compounds. The vegetable world is the laboratory, where 
this subtle chemistry is carried forward, and matter takes on the 
properties of organization. Such is the ultimate source of all our 
food. The solid materials which we perpetually incorporate into the 
Dodily fabric, originated in plants, under the direct agency of the sun- 



20G SOURCE OF ALIMENTS ORDER OF THE SUBJECT. 

beam. The vegetable leaf is the crucible of vitality, the consecrated 
mechanism appointed to receive the life-forces which God is per- 
petually pouring througli his universe.- In partaking of the bounties 
of the table, are we not, then, consummating a purpose to which 
planetary systems are subservient ? "We repair the failing textures of 
animal life, but it is with tissues woven in a loom of invisible airs by 
the flying shuttles of light. That a single grain of wheat may be 
ripened — that its constituent starch, gluten and sugar may be per- 
fected, this ponderous orb must shoot along the ecliptic at the rate 
of 68,000 miles per hour, from Taurus to Libra, whirling perpetually 
upon its axis as it tlies, that all parts may receive, alike the vitalizing 
radiations. When therefore we contemplate the grandeur of the 
operations by which the Creator accomplishes the problem of life in 
this state of being, the subject of foods rises to a transcendent interest. 
The consideration of these questions, however, the forces that control 
vegetable growth and give rise to organic compounds, pertains to 
chemistry and vegetable physiology ; neither our plan nor our space 
will allow us to consider them here. We direct attention first to the 
general properties of foods, as we find them already produced and 
presented for preparation and use. 

365. How Foods may be considered. — A systematic presentation of 
the subject of aliments, that shall be quite free fi'om scientific objec- 
tion, appears in the present state of knowledge to be impossible. We 
shall adopt an arrangement which aims only to be simple and popular. 
All articles of diet are composed of certain substances, which are 
known a.?, alimentary principles, — simple aliments, audi proximate prin- 
ciples. These are not the ultimate elements, carbon, oxygen, hydro- 
den, nitrogen, sulphur, dec, but are formed by combinations of these. 
They difi:er from each other in properties, exist in very different 
proportions in various kinds of food, and are capable of being sepa- 
rated from each other and examined independently. These require to 
be first considered. Next in order we shall speak of tlie products 
whichi these simple principles form when united together. Thus 
starch, sugar, gluten, &c., are simple aliments; while grain, roots, 
meats, &c., are made up of them, and are therefore called compound 
aliments. We shall give the composition of these, and as much of 
their history and preparation as may be necessary to understand their 
properties, and then ti'ace the changes which they undergo in culinary 
management. The principles involved in various modes of preserving 
alimentary substances will next be described, and the subject closed 
by an examination of their physiological effects and nutritive powers. 



WATER — ITS SOLVENT PEOPERTIES. 207 

366. Division of Alimentary PrinclplcSt — The simple alimentary prin- 
ciples are separated into two important divisions, based on their com- 
position ; firsts the non-nitrogenous aliments, or those containing no 
nitrogen in their composition ; and second^ the nitrogenous aliments^ 
or those which do contain this element. The first group consists of 
starch, sugar, gum, oil, and vegetable acids ; while the second com- 
prise albumen, fibrin, gluten, casein. Of these two classes the first 
is simpler in composition and much more abundant in nature than the 
other class ; we shall hence consider them first. There is, however, 
anotlier alimentary substance of peculiar properties, and of the first 
importance — water, which cannot be ranked strictly with either group. 
It is not a product of vegetable gi-owth, but is rather a kind of univer- 
sal medium or instrument of all sorts of organic changes. As the 
most abundant and indispensable of all the principles of diet, it claims 
our first attention. 

II.— GENERAL PROPERTIES OF ALIMENTARY SUBSTANCES. 

1. PeINOIPLES CoNTAININa NO NlTEOGEN. 
A.— Water. 

367. SolTent Powers of Water, — One of the most important proper- 
ties of water is its wonderful poAver of dissolving many solids ; that 
is, when placed within it they lose their solid form, disappear, and be- 
come difi'used through the liquid. Such a combination is called solu- 
tion. It is the result of a mutual attraction between the liquid and 
the solid, and it becomes weaker between the two substances as this 
attraction is satisfied. The action of water upon soluble substances is 
very powerful at first, but as solution proceeds the action gradually de- 
creases, until the water wiU dissolve no more; it is then said to bo 
saturated. "Water saturated with one substance, may lose a portion ol 
its power to dissolve others, or its solvent energy may sometimes be 
increased ; this depends upon the compound which it contains in solu- 
tion. With some substances it combines in all proportions, and never 
gets saturated. Water does not dissolve a?? substances ; if a fragment 
of glass and a piece of salt be put into it, the glass will be unchanged, 
while the salt will vanish and become liquid. Nor does it dissolve 
alilce all that it acts upon ; a pound of cold water will dissolve two 
pounds of sugar, while it will take up not over six ounces of common 
salt, two and a half of alum, and not more than eight grains of lime. 
Heat influences the solvent powers of water, most generally increasing 
it; thus, boiling water will dissolve 17 times as much saltpetre as ice 



208 GENERAL PROPERTIES OF ALIMENTARY SUBSTANCES. 

water. This it seeras to do by repelling the particles of the solid body 
from each other, thus assisting the water to insinuate itself among 
them, by Avhich its action is helped. But there are exceptions to the 
rule, of which lime is an example ; sixty-six gallons of water at 32*^ 
dissolves one lb. of lime, but it takes 75 gallons at 60°, or 128 at 212°, 
to produce the same effect, so that ice-cold water dissolves twice as 
mucli lime as boiling Avater. 

368. How best to hasten Solotion. — Solids should be crushed or 
pulverized, to expose the largest surface to the action of the solvent 
liquid. Substances which in the lump would remain for days undis- 
solved, when reduced to powder are liquefied in a short time. When 
a solid, as common salt or alum, is placed in a vessel of water to dis- 
solve, it rests at the bottom. The water surrounding it becomes sat- 
urated, and being heavier, remains also at the bottom, so that the solu- 
tion proceeds very slowly. By stirring, the action is hastened, but this 
takes up much time. The best plan is to suspend the salt in a colan- 
der, basket, or coarse bag, at the surface of the liquid. As the parti- 
cles of water take up the particles of salt, they become heavier and 
sink ; other particles take their places, dissolve more of the salt, and 
sink in turn, so that the action of a constant current of liquid is kept 
up on the suspended crystals, and always at that portion most capable 
of dissolving them. 

369. Solntion of Gases — Soda-water. — Water also dissolves or absorbs 
various gases, some more and some less. It may take 780 times its 
bulk of ammonia, an equal bulk of carbonic acid, or ^3 its bulk of 
oxygen. The quantity is, however, controlled by heat and pressure ; 
heat acts to expel the gases, so that as the temperature rises, the water 
will hold less and less, while with increased pressure, on the contrary, 
it will receive an increased amount. Soda-water is thus by pressure 
overcharged with carbonic acid gas, which escapes with violent effer- 
vescence when the pressure is withdrawn. The effect is the same, 
whether the gas is forced into the Avater from without, or generated in 
a tight bottle or other vessel, as is the case with fermented liquors. 
The gas gradually produced is dissolved by the water, which, escaping 
when the cork is withdrawn or the vessel unclosed, produces the foam- 
ing and briskness of the liquor. 

370. Different varieties of Water. — In nature water comes in contact 
with a great number of substances which it dissolves, so that there is 
consequently no perfectly pure, natural water. The substances which 

t takes up are numerous, and differ under various circumstances and 
eonditions, and as these foreign substances or impurities which the 



THE GASES DISSOLVED IN WATEK. 209 

•water acquires, communicate tlieir properties to the liquid, it results 
that tliere are many varieties of natural water, as for example, spring- 
water, river-water, sea-water, rain-water, &c. 

371. Raitt-water and Saow-water. — Rain-water is the least contami- 
nated of all natural waters, yet it is hy no means perfectly pure. As 
it falls through the air, it absorbs oxygen, nitrogen, carbonic acid 
and ammonia, with which it comes in contact, and it also washes out 
of the atmosphere whatever impurities it may happen to contain. 
Thus, in the vicinity of the ocean, the air contains a trace of common 
salt ; in the neighborhood of cities, various saline, organic, and gaseous 
impurities, while dust is raised from the ground and scattered through 
it by winds, and these are all rinsed out of the air by rains. The 
water which falls first after a period of drought, when contaminations 
have accumulated in the air for some time, is most impure. Eain fall- 
ing in the country, away from houses, and at the close of protracted 
storms, is the purest water that nature provides. It diifers from dis- 
tilled water only in being aerated, that is, charged with the natural 
gases of the air. Falling near houses, it collects the smoky exhala- 
tions, and flowing over the roofs it carries down the deposited soot, 
dust, &c. Water from melted snow is purer than rain-water, as it de- 
scends through the air in a solid form, incapable of absorbing atmos- 
pheric gases. When melted, the water which it produces is insipid 
from their absence, and should be exposed for a day or two to the at- 
mosphere, that it may absorb them. 

372. The Gases contained in Water. There is an atmosphere diffused 
through all natural waters. It is richer in oxygen than is the upper 
atmosphere ; in the latter there is but 23 per cent., while in the air ot 
water there is 33 per cent. The animals which dwell in water absorb 
this oxygen by breathing, just as land animals do from the air, while 
water-plants in the same manner live on the carbonic acid it contains. 
These absorbed gases also influence its taste, giving it a brisk and 
agreeable flavor. If it is boiled they are driven off, and the liquid be- 
comes flat and mawkish. The presence of as much oxygen as water 
will hold, improves it as a beverage, as this gas is necessary to the ac- 
tive performance of several of the most important vital functions. 
Water that is quite cold contains more oxygen than that which has 
been made warm in any way, as by exposure to the sun or the warmth 
of a close room, which causes a portion of it to escape. 

373. Organic Contaminations of Water. — From the dust and insects 
of the air, the wash of the ground and the drainage of residences, 
from mud and decayed leaves, the decomposing bodies of dead ani- 



210 GENERAL PROPEKTIES OF ALIMENTARY SUBSTANCES. 

mals, and a variety of other causes, waters are liable to conta //- 
ganic impurities, or those vestiges of living structures whic'i are 
capable of decomposition and putrefactive change. The effect of this 
organic matter may be sliown by taking a little of the sediment that 
has accumulated at the bottom of a cistern, and placing it in a bottle 
of perfectly pure distilled water, when in a short time, if the weathei 
be warm, it will begin to smell offensively. This kind of contamina- 
tion may be either suspended mechanically in water as solid particles, 
or it may be dissolved in it so that the water shaU still have an appear- 
ance of purity. 

874. The living Inhabitauts of Water. — Under certain favorable con- 
ditions of warmth, access of air, light, &c., countless numbers of living 
beings, both plants and animals, make their appearance in water. 
They are nourished upon the dead organic matter which the water 
may happen to contain, and belong either to the animal kingdom as 
animalcula or infusoria, or are of a vegetable nature, as fungi. 
There are other conditions which influence the hind of life which ap- 
pears in water. If the liquid be slightly alkaline, animalcula will be 
produced, while if it be a little acid, fungi or microscopic plants will 
ai)pear. This may be shown by diffusing a little white of egg through 
water in a wine glass, and keeping it in a warm place. If ft be made 
in a small degree alkaline, it wiU swarm with animalcula in a few days ; 
if, on the contrary, it be slightly acid, vegetable forms wiU be princi- 
pally originated. It is important to notice also that the alkaline solution 
will run rapidly into putrefaction, and yield a putrescent smell, while 
the acid fluid will scarcely alter at all, and emit no unpleasant odor. 
It is hence obvious that these two kinds of water have different I'ela- 
tions to human health, the slightly acid being more favorable to it 
than alkaline waters. These living inhabitants are never found in 
freshly fallen rain-water, caught at a distance from houses, nor in 
spring or well-water, but they more or less abound in cistern water, 
reservoir water, and marsh, pond, and river waters. 

375. Tse of living beings in impure Water. — The presence of living 
tribes in impure water, fulfils a wise and beneficent purpose. If the 
large amount of organic matter present in many waters could bo re- 
moved only by the common process of putrefaction, and the forma- 
tion of injurious compounds and offensive gases, immense mischief 
would be the consequence. To obviate this, nature has ordained that 
some of the organic matter of impure water, in place of undergoing 
decomposition, shall be imbibed by living beings, and these dpng that 
others shall take their place and fulfil the same important office. The 



MINERAI, MATTER DISSOLVED BY WATER, 211 

iiving races tlms exert a preservative influence upon water, although 
this is more especially true of aquatic vegetation. 

376. WJiter dissolves variable quantities of Mineral Matter. — Rain 
which falls upon high ground filters through the porous soil and strata 
of the earth until stopped by impenetrable clay or rock ; it then passes 
along the surface of the bed until it finds an opening or crevice, 
through which it is forced up to the surface of the ground, producing 
a spring. Water which has thus leached through the mineral mate- 
rials of the earth, dissolves such portions of its soluble materials as it 
meets with, and carries them down to the lower levels, so that they 
ultimately collect in the sea. Tlie amount of muieral matter thus dis- 
solved is extremely various. The water of the river Loka, in North- 
ern Sweden, which flows over impervious, insoluble granite, contains 
only gV of a grain of mineral matter in a gallon weighing 70,000 
grains. Common well-waters, spring-water and river-water, contain 
from 5 to 60 grains in a gallon, but generally, in waters of average 
purity, which are employed for domestic purposes, there are not pres- 
ent more than 20 or 30 grains of mineral matter to the gallon. When 
the dissolved substances accumulate until they can be tasted, a mineral 
water results. The celebrated Congress water, at Saratoga, contains 
611 grains to the gallon. Ocean water has as much as 2,500 grains of 
saline substances, and the water of the Dead Sea the enormous quan- 
tity of 20,000 grains in the gallon. Of the two natural waters — those 
of the river Loka and the Dead Sea — the latter contains 400,000 times 
more saline matter than the former. 

877. Rinds of Mineral Matter dissolved ty Water. — The mineral sub- 
stances dissolved in spring and well waters, are chiefly iron, soda, 
magnesia and hrae, combined with carbonic and sulphuric acids, and 
forming salts^ which are compounds of acids with alkalies or bases ; 
sulphates and carbonates, together with chloride of sodium or common 
salt. Iron, mixed with carbonic and sulphuric acids, is present in 
most waters which percolate through the ground; soda and magnesia 
also often exist in these waters, but their most universal and important 
ingredient is lime. This exists in almost all soils in combination with 
carbonic acid as carbonate of lime, or powdered limestone, and it is 
also very common in the shape of sulphate of lime, or plaster. Most 
of these substances are soluble in pure water, but this is not the case 
with the widely diffused carbonate of lime. The power of dissolving 
this substance depends upon the presence of free carbonic acid con- 
tained within in the water. If charged with this gas, water beconwjs 
a solvent of limestone. 



212 GEXERAL PROPERTIES OP ALIMENTARY SUBSTANCES. 

378. Hard and Soft Water. — The presence in Wcater of these dis- 
solved mineral substiinces, though in extremely small proportit)n, pro- 
duces important changes in its properties. Compounds of lime and 
magnesia give it Jiardness^ while rain and snow-water, and that from 
some springs which are free from these mineral matters, are called 
soft. This distinction of waters into hard and soft is usually connected 
with its cleansing qualities and its behavior towards soap, which wo 
shall consider in another place. It is also important dietetically (533). 

379. Water in contact with Lead. — There has been much contradic- 
aon among scientific men in regard to the effects of storing water in 
leaden vessels, or transmitting it through leaden pipes. It was known 
that some kinds of water would corrode or dissolve the lead and be- 
come poisonous ; but what waters? Dr. Cheistison said those which 
were soft^ while hard waters would form a crust in the interior surface 
of the lead, and thus protect it from cori-osion. But later experi- 
menters declare hard waters to be even worse than soft in their action 
upon lead. It may be remarked that water can act upon lead, cor- 
roding it without becoming itself actively poisonous, if the compound 
formed be huoluble ; it is only when the lead is dissolved that the 
water containing it becomes dangerous. "When ordinary water is 
placed in contact with lead, the free oxygen it contains combines with 
the metal, forming oxide of lead ; water immediately unites with that 
producing hydrated oxide of lead, which is nearly insoluble in water. 
There is also more or less carbonic acid existing in all natural waters; 
this combines with the oxide of lead, forming carbonate of lead, 
which is also highly insoluble. But if there be in the water rmich 
carbonic acid, a hicarlonate of lead is formed, which is very soluble, 
and therefore remains dissolved in the water. Hence waters which 
abound in free carbonic acid, as aiso those which contain hi carbonates 
of lime, magnesia, and potash, are most liable to become poisoned by 
lead. "Water containing common salt acts upon this metal, forming & 
soluble, poisonous chloride of lead. On the other hand, water con- 
taining sulphates and phosphates is but little injured, these salts exert- 
ing a protective influence on the lead. " From a review therefore of 
the whole of the arguments and experiments now advanced, respect- 
ing the action of diiFerent waters on lead, we deduce the following 
general conclusions : That while very soft water cannot be stored for 
a lengthened period, with impunity, in leaden vessels, the danger of 
the storage of hard water under the same circumstances is in most 
cases much greater. This danger, however, is to be estimated neither 
by the qualities of hardness or softness, but altogether depends upon 



SOFT WATER STAECH. 



213 



the chemical constitution of each different kind of water ; thus, if this 
be ever so soft, and contain free carbonic acid, its action on lead will 
be great ; whereas if it be hard from the presence of sulphates and 
phosphates principally, and contain but few bicarbonates, &c., little 
or no solution of the lead wiU result." — ^Dr. Hassall. "Water is 
powerfully corrosive of iron when conveyed through this metal in 
pipes, but the compounds formed are not injurious. Galvanized iron 
pipes, which have received a coating of tin (610), are coming much 
into use instead of lead for the conveyance of water. 

380. Supply of Soft Water. — "WeUs and springs are often inacessible, 
or the water furnished is bad. In such cases the heavens furnish an 
unfailing resource, which, with well-constructed cisterns, filters, and 
ice, leave little to be <lesired in the way of aqueous luxury. Taking 
the annual rainfiiU at 36 inches, we have 3 cubic feet of water falling 
upon a square foot of surface in a year. A cubic foot contains 6|- 
gallons, so that we get 18 J gallons upon each surface foot annually. 
A house 25 by 40 has a thousand feet of surface, and collects nearly 
19,000 gallons of water annually, which if stored in cisterns of suf- 
ficient capacity, will furnish more than 50 gallons per day throughout 
the year. 

B.— The Starcbes. 

381. AVlience obtained, and how separated. — Starch, when pure, is 
seen to be a fine snow-white glistening powder. It is found univer 
sally distributed in the vege- 
table kingdom in much 
greater quantity than any 
other substance formed by 
plants for food. It exists 
in grain, peas and beans ; in 
all kinds of seeds ; in roots, 
as potatoes and carrots, and 
in the stem, pith, bark, and 
fruit ©f many plants. When 
wheat flour is mixed up into 
a dough, and washed (Fig. 
88), on a linen cloth with 
clean water, a milky liquid 
passes through contaiuing 
wlieat starch, which grad- 
ually settles to the bottom 



FiQ. 88. 




T7 

Scparatin 



1 \r^ II 

starch from Hour by washing. 



of the vessel. If raw potatoes are 



214 GENERAL PROPERTIES OF ALIMENTARY SUBSTANCES. 



grated, and the pulp treated in a similar manner, potato starch is 
separated. 

882. Proportions in yarions substances. — The variable proportion of 
starch in difterent articles of food is as follows, in decreasing order: 

Starch per cent. 

Kice flour 84 to 85 

IniUan corn 77 to 80 

Oatmeal 70 to 80 

Wheat flour 39 to 77 

Barley flour G7 to 70 

Rye flour 50 to 61 

Buckwheat 52 

Pea and bean meal 42 to 43 

Potatoes, containing 73 to 73 water, ■. 13 to 15 

383. Starch Grains — their size. — Starch consists of exceedingly small 
rounded grains. They cannot be distinctly seen with the naked 
eye, and are so extremely minute that the finest wheat flour, which 
has been ground to an impalpable dust, contains its starch graina 
mostly unbroken and perfect. The granules of potato starch aro 
largest, while those of wheat and rice are much smaller (Fig. 89), and 
those of turnips and parsnips still smaller, varying all the way from 

Fig. 89. 

/^^^mf% i , , .„\ ^'^ ..%«.* 

starch-grains of potatoes. Starch-grains of piantain. Starch-grains of rice, 

tlie 1 -300th to 1-10, 000th of an inch in diameter. Assuming the 
grains of wheat starch to bo 1-lOOOth of an inch in diameter, a thou- 
sand million of them would bo contained in a cubic inch of space. 

384. Their Appearance and Strnctnre. — Viewed under a high mag- 
nifier, starch grains from various sources exhibit marked peculiaritiea 
in form as well as in size. Several kinds have a ringed or grooved 
aspect, as seen in Fig. 89, which appearance is explained by the fact 
that they consist of concentric layers or membranes, like the coats 



DITTEKENT VARIETIES OF STARCH. 215 

cf an onion. The grains of potato starch are ovoid or egg-shaped. 
Many of the grains of pea starch ai-e hollowed or concave in the direc- 
tion of their length, while wheat starch consists of dull, flattened, 
lens-shaped grains, sticking together when not perfectly dry, on 
which account the wheat starch of commerce always comes in loose 
lumps. Thus each variety of starch-grain has some peculiar appeai*- 
ance of its own, by which the practical microscopist is enabled to 
identify it. He can hence detect adulterations of the more valuable 
with the cheaper varieties, as wheaten flour or maranta arrow-root 
with potato starch. 

385. Sago StarcU is procured from the pith of several varieties of 
the palm tree. It comes in various forms. Sago meal or flour is a 
whitish powder. Pearl-sago, the kind in general use for domestic 
purposes, consists of small pinkish or yellowish grains, about the size 
of a pin's head. Common or brown sago consists of much larger 
grains, which are of a brownish white color, each grain being brownish 
on one side and whitish on the other. As all the kinds of sago contain 
coloring matters, they are considered inferior to those varieties of 
starch, as arrow-root and tapioca, which are perfectly white. 

386. Tapioca is a variety of starch which comes from South Ameri- 
ca, and is obtained from the root of a plant containing a poisonous 
milky juice. When it appears as a white powder, it is called Brazil- 
ian arrow-root. The term tapioca is commonly applied to that form 
of it which appears in small irregular lumps, caused by its having 
been dried on hot plates, and then broken up into fragments. 

387. Arrow-roct. — A root growing in the West Indies (the Maranta 
arundinacea), contained a juice supposed to be capable of counter- 
acting the effects of wounds inflicted by poisonous arrows. This root 
yielded a starch which took the name of maranta arrow-root. But 
afterward starches from other plants which liad a resemblance to 
maranta starch, took also the name of arrow-roots. Thus there Is 
Tahiti arrow-root, Manihot arrow-root, from the plant which yields 
tapioca, and potato arrow-root, or British arrow-root, as it is some- 
times called. Maranta arrow-root, which is a very pure white starchy 
powder, is the most prized of all the varieties, but it is often adulter- 
ated with other and cheaper kinds. 

388. Corn Starcb. — This is a preparation of the starch of Indian 
corn, which has been separatectas perfectly as possible from the otlier 
constituents of the grain. Chemical means are used to effect the 
separation. The starch is freed from the glutinous, oily and ligneous 
elements of the seed, by the aid of alkaline solutions, and by grinding 



21G GENERAL PKOPEKTIES OF ALIMENTARY SUBSTANCES. 

and bolting the corn in a wet condition. The grain is reported to 
yield from 30 to 35 per cent, of pure starch, which bears a general 
price, about one-third greater than wheaten flour. The culinary 
changes of starch and its effects upon the system will be considered 
under these topics (51G). 

889. Chemical Composition. — Starch consists of three elements, — 
carbon or charcoal, oxygen, and hydrogen. The two latter are found 
in starch in exactly the same proportions that they exist in water, so 
that the composition of this substance may be given as simply char- 
coal and water. A compound atom of starch consists of twelve atoms 
of carbon, combined with ten of oxygen and ten of hydrogen, or 
twelve atoms of carbon to ten of water. 

C— The Siig-ars. 

390. Proportion In various Substances. — This is the sweet principle 
of food, and is produced by both plants and animals. It exists in 
milk, and it has lately been shown that it is generated in the animal 
liver. But our supplies come entirely from the vegetable world, 
where it is produced in great abundance, both in the sap and juices 
of plants, and stored up in their fruits and seeds. The following is 
the proportion of sugar obtainable from various sources : 

Ter cent, of Sugar. 

Juice of Sugar cane 12 to 13 

Beet root 5 to 9 

Wheat flour 4 to 6 

Barley moal 5"2 

Oat meal 4-8 

Cow's milk S-8 

Eye meal 8-2 

Peas 2 

Indian corn 1'5 

Rice "2 

There are several varieties of sugar, but we are practically concerned 
with but two, cane sugar and grape sugar. 

391. Grape Sugar or Fruit Sugar. — The white sweet grains of raisins 
or dried grapes take the name of grape sugar. Most other fruits, 
however, as apples, pears, plums, figs, cherries, peaches, gooseberries, 
currants, &c., groAv sweet in ripening, which is owing to the same 
kind of sugar which exists in the grape. It may be readily extracted 
from fruits, but this is rarely done. * 

392. Sugar Artificially Produced. — If starch be boiled for some time 
in water wliich has been soured by adding to it one or two per cent, 
of sulphuric acid, the solution gradually acquires a sweet taste. If, 



PKODUCTION ANB COMPOSITION OF HONEY. 217 

now, by suitable means, the acid be neutralized and removed, and tlie 
Bolution boiled down, it yields a rich sirup or a solid sugar. This 
comes from the transformation of starch ; the acid taking no direct 
part in the change, but only indiacing it by its presence. Potatoes 
treated ia this way, it is said, will produce ten per cent, of their weight 
of sugar. But what is still more singular, the fibre of wood may also 
be converted into sugar. Paper, raw cotton, flax, linen and cotton 
rags, and even sawdust, may be changed to sugar by the same agency. 
The boiling with acid must, however, in this case, be continued longer, 
as the woody matter has first to be changed to starch before it be- 
comes sugar. This product, known as starch sugar, has the samo 
nature and properties as grape sugar. 

393. Honey. — This is obtained by bees from the juices found in the 
nectaries, or honey-cups of flowers. They collect it in the crop, or 
honey-bag, which is an enlargement of the gullet, and when filled is 
about the size of a pea. Laden with its sweet treasure, the insect 
returns to the hive and disgorges it into a previously prepared cell of 
the honeycomb, which it then caps over by a thin covering of wax. 
To procure it in the purest liquid form, and of the best flavor, the 
plan is to unseal the cells by removing a slice from the surface of the 
comb, after which it is laid upon a cullender to drain. It is some- 
times warmed, to facilitate the flowing, but this is said to injure the 
delicacy of its flavor. It is more commonly pressed. This increases 
the quantity, and saves time ; but it is then contaminated by traces 
of wax, and fouled by the juices of ci'ushed bee-maggots, which may 
happen to be in the comb. 

394. Properties and Composition. — Honey, in different localities, differ- 
ent seasons, and from different flowers, varies very much in color, flavor, 
and fragrance. That from clover, or from highly fragrant flowers, is far 
superior to that from buckwheat ; spring-made honey is better than 
that produced in autumn. Virgin honey, or that made from bees 
that never swarmed, is finer than that yielded by older swarms ; and 
while some regions are renowned for the exquisite and unrivalled 
flavor of their honeys, that made in some other places is actually 
poisonous. "We can hardly suppose honey to be a simple vegetable 
liquid. It probably undergoes some change in the body of the insect 
by the action of the juices of the mouth and crop, as when bees are 
fed upon common sugar alone they produce honey. Honey is an in- 
tensely sweet sirup, varying in color from nearly white to a yellowish 
brown. It consists of two sorts of sugar. One of these remains always 
in a liquid or sirupy condition, and the other is liable to crystallize or 

10 



218 GENEEAL PROPERTIES OF ALIIIENTARY SUBSTANCES. 

change to solid grains (granulate), this is grape sugar. The lightest 
colored and most valuable honeys contain the most of it, and henca 
are most liable to granulate and grow thick. Honey contains an 
acid, and aromatic principles, which together with its uncrystallizable 
Bweet part, are not very well understood. 

395. Cane Sngar — its Sonrees. — Our common sugar is obtained, as is 
well known, from the sugar-cane. Eleven-twelfths of all the sugar 
of commerce has this origin. That which is procured from the as- 
cending sap of the maple, the descending sap of the birch, and also 
from the walnut and other trees ; from the juice of beets, carrots, 
turnips and melons, from green corn-stalks, and the unripe seeds of 
grain, is identical in essential properties with that of the sugar-cane, 
and they are all distinguished as cane sugar. 

396. Cane and Grape Sngars, different conditions of origin. — It is teces- 
sary to understand clearly the difterence between cane sugar and grape 
sugar. We have seen that the agency of acids is employed to convert 
starch into grape sugar, and they have the same eifect upon cane 
sugar. This change takes place even in the interior of growing 
plants. Those plants and fruits which possess sour or acid juices, yield 
grape sugar, while those which contain little or no acid in their saps, 
contain generally cane sugar. Grape sugar may be produced by art, 
while cane sugar cannot. 

397. Cane and Grape Sugars, chemical differences. — Sugar, like starch, 
consists only of carbon and water ; but these two sugars diflfer in the 
proportion of these elements. "While cane sugar contains twelve 
atoms of carbon to eleven of water, grape sugar contains twelve atoms 
of carbon to fourteen of water. Grape sugar is therefore less rich in 
carbon than cane sugar, and cane sugar may be transformed into 
grape sugar by the addition of chemically combined water. It is an 
essential property of sugar, that under the action of ferments, they are 
decomposed ; converted into carbonic acid and alcohol. Grape sugar 
is most prone to this change ; and cane sugar, before it can undergo 
fei'mcntation, must be first changed into grape sugar. Cane sugar 
passes into the solid state much more readily than grape sugar, taking 
on the form of clear, well defined crystals of a constant figure ; grape 
sugar, on the contrary, crystallizes reluctantly and imperfectly, with- 
out constancy or form. Crystals of cane sugar are regular six-sided 
figures, while those of grape sugar are ill-defined, needle-shaped 
tufts. 

898. Difference of solubility and sweetening powers. — Pure cane sugar 
remains perfectly dry and unchanged in the air, while grape sugar 



PBODUCTTON OF COAitSE SUGAR. 219 

attracts atmospheric moisture, becoming mealy and damp. Yet cane 
BUgar dissolves in water much more readily than grape sugar. "While 
a pound of cold water will dissolve three pounds of the formei-, it will 
take up but two-thirds of a pound of the latter. Cane sugar will, 
therefore, make a much thicker and stronger sirup than grape sugar, 
dissolving also more freely in the juices of the mouth, (a property 
upon which taste depends). Cane sugar possesses a higher sweetening 
power than the other variety. Powdered grape sugar has a floury 
taste when placed upon the tongue, and very gradually becomes 
sweet and gummy or mucilaginous as it dissolves. Two parts by 
weight of cane sugar are considered to go as far in sweetening as 
five of grape sugar. To make them economically equal, therefore, 
five pounds of grape sugar should cost only as much as two of cane 
sugar ; and hence the mingling of grape with cane sugar is a serious 
deterioration of it. 

399. How Raw, oi; Browa Sugar isprodaced. — The sugar of commerce 
appears in various forms, and is sold at various prices. It is impor- 
tant to inquire into the source of these differences which involves a 
reference to the manufacture. Cane-juice contains vegetable albu- 
men, a substance which has a strong tendency to fermentation (488), 
hence, when left to itself in warm climates, it is rapidly changed ; the 
acid of vinegar being generated ; — twenty minutes is, in many cases, 
sufficient to produce this effect. To neutralize any acid that may be 
thus formed, and partially to clarify the crude juice, lime, Avhich has a 
powerful attraction for organic matter, is added. The juice is then 
boiled, the water being evaporated away xmtil a sirup is produced. 
The liquid is then drawn off into shallow vessels and stirred. As it 
cools the sugar granulates^ or appears in the form of small irregular 
grains or crystals, which are kept from uniting together by some of 
the sirup (which has been so altered by the heat that it refuses to 
crystallize), and is known as molasses. The product is then placed in 
suitable circumstances to drain, when a large portion of the molasses 
flows away, and is collected in separate vessels. The sugar, packed in 
hogsheads, is then sent to the market as raw or muscovado, or as it is 
more commonly known, as troion sugar. 

400. Of what Brown Sugar consists. — The article when packed by 
'the sugar-boiler, consists of sugar more or less browned and dampened 
by molasses, according to the completeness of the draining and dry- 
ing process. It contains more or less vegetable albumen, lime from 
the added lime-water, minute fragments of crushed cane-stalks, often 
in considerable quantity, with grit or sand from the unwashed canes, 



220 CxENERAL PROPERTIES OF ALIMENTARY SUBSTANCES. 



Fig 



or -which may have been introduced into the granulating vessels by 
careless management. 

401. Brown Sugar undergoes a slow fermentation, — We have stated 
that albumen is a A-ery changeable substance, and by its own decompo- 
sition, when in contact with sugar, tends to alter that also. Cane 
sugar, it transforms into grape sugar. Hence, in nearly all raw sugars, 
there is an incipient, slow fermentation going forward, by which a 
portion of cane sugar is converted into grape sugar. Dr. Hassall, 
perhaps the highest authority in matters pertaining to alimentary im- 
purities, states that nearly all samples of brown sugar contain also 
grape sugar, and that its proportion is greater where there is most 
vegetable albumen. This change, of course, just according to its ex- 
tent, lowers the value of brown sugar. 

402. Living eontaminations of Brown Sugar. — We had occasion, when 
speaking of water, to correct that common impression of the ill-in- 
formed, that swarms of animalculjB are present in every thing we eat 
and drink. On the contrary, they exist only in certain circumstan 
ces, and Avhen they do occur, of course impair the value of food for 
dietetical use. As all animal structures, from the largest to the 

smallest contain nitrogen, one 
of the conditions of the exist- 
ence of animalcula3 is the pres- 
ence of nitrogeneous matter 
upon which to feed. Now pure 
sugar contains no nitrogen, and 
therefore cannot sustain animal 
life. But in brown, coarse 
sugars the existence of vegeta- 
ble albumen offers nourishment 
to these beings, and accordingly 
they are commonly found in- 
fested with minute insects called 
sugar-mites. In general, the 
more the sugar is contaminated 
with albumen, the more numer- 
ous are these disgusting insects. 
They may be detected in the 
less pure sugars by dissolving two or three tea-spoonfuls in a large 
wine-glass of tepid water. After standing at rest an hour or two, the 
animalculfo will be found, some on the surface of the liquid, some ad- 
hering to the sides of the glass, and some in the dark sediment at 




Sugar-mite, as seen upon a fraprment of cane, 
magnifiod 180 diameters. 



MOLASSES — SUGAK-REFINING. 221 

the bottom, mixed with caiie-fragments, grit, and dirt. The mite ia 
visible to the naked eye, as a mere speck ; the microscope, however, 
exhibits its appearance, and history, from the egg state to the per- 
fectly developed animal, which is represented in Fig. W). 

403. Properties and Compositioa of Molasses. — Common molasses is a 
dense brown liquid, the drainage of the brown sugar manufacture. It 
contains a portion of sugar that has been burnt and darkened in boil- 
ing ; another part that has been so changed to the mucilaginous state, 
by boiling, that it does not crystallize, together with a quantity of 
crystallizable sugar. It is strongly absorbent of water ; indeed, many 
kinds of raw sugar melt into sirup when exposed to the air. Chemi- 
cally considered sugar is an acid substance, and combines with bases, 
as potash, soda, magnesia, to form salts caUed saccharates. Molasses 
contains a portion of saccharine matter, combined with the lime used 
in the sugar manufacture (399) ; also with small quantities of the alka- 
lies. Molasses itself is also acidulous. It has a peculiar strong taste, 
which Cadet states may be removed by boiling for half an hour with 
pulverized charcoal. Sugar-Jiouse molasses and sirups are the residue 
which remains uncrystallized in purifying and refining brown sugar. 

404. Refined Sugar. — To cleanse it of impurities and improve it in 
color and taste, crude sugar is refined. It is melted and has mingled 
with it a small portion of albumen (ox-blood), which clears it of me- 
chanical contaminations. The sirup is then filtered through a bed ol 
animal charcoal (burnt bones crushed), by which it is decolorized, and 
lastly, it is crystallized, by boiling at a low temperature in vacuum- 
pans, in which the atmospheric pressure is removed (62). The discol- 
oring and darkening principle in the various grades of sugar is the 
molasses which has not been removed, but which remains in the crys- 
tallized mass. 

405. Sngar-eandy and how it is Colored. — When the pure sugar is melted 
or dissolved, it forms a clear liquid, and when allowed to cool or dry 
without disturbance, it crystallizes into a transparent solid, like glass. 
When threads are suspended in the sngar solution, crystals of extreme 
hardness collect upon them, which are known as rock-candy. The 
cause of whiteness in refined sugar is that the crystals are small, con- 
fused, and irregular. To make candy white, the sugar, Avhile cooling, 
is agitated and worked (pulled), which breaks up the crystals and ren- 
ders the mass opaque. Candy is commonly adulterated with flour, 
and frequently with chalk. Various colors are given to sugar-confec- 
tionery by adding paints and dies expressly for the purpose. Some of 
these are harmless and others poisonous. Those which are least inju- 



222 GEXEUAL PROPERTIES OP ALIMENTARY SUBSTANCES. 

rious are the vegetable and animal coloring matters, but these neither 
form so brilliant colors nor are they so lasting as the mineral com- 
pounds, which are far the most deadly. The following are the chief 
coloring substances used by confectioners to beautify their sugar 
preparations : 

( Oxide of lead (recJ lead). 

Reds ) Bisulphuret of mercury {vermilion'). 

( Bisulphuret of arsenic {red orpimenf). 

t Gamboge. 

Yellows. . . < Chromate of lead {chrome yellow). 

( Sulphuret of arsenic {yellow orpimenf). 

( Ferrocyanide of iron {Prussian blue). 

j Cobalt. 

Blues -j Smalt {glass of cohalf). 

I Carbonate of copper {verditer). 

{, Ultramarine. 

( Diacetate of copper {verdigris). 

Gkeenb ■} Arsenite of copper {emerald green . 

( Carbonate of copper {mineral green). 

"Whites Carbon.ite of lead {lohite lead). 

PuKPLES Formed by combining blues and reds. 

From an examination of 101 samples of London confectionery, Dr. 
Hassall found that 59 samples of yellow were colored with chromate 
of lead and 11 with gamboge. That of the reds 61 were colored with 
cocldneal.1 12 with red lead., and 6 with vermilion. Of the blues, one 
sample was colored by indigo, 22 by Prussian line, and 15 by ultra- 
marine. Of the greens 10 were colored by a mixture of chromate oj 
lead and Prussian Mue, 1 with carionate of copper., and 9 with arsen 
ite of copper. These colors were variously combined in the different 
cases, as many as from three to seven colors occurring in the same 
parcel, including three or four poisons. 

406. Their dangerous and fatal Effects. — The Dr. remarks: "It may 
be alleged by some that these substances are employed in quantities 
too inconsiderable to prove injurious, but this is certainly not so, for 
the quantity used, as is amply indicated in many cases by the eye 
alone, is often very large, and suflBcient, as is proved by numberless re- 
corded and continually recurring instances, to occasion disease and 
death. It should be remembered, too, that these preparations of lead, 
mercury, copper, and arsenic, are what are termed cumulative., that is, 
they are liable to accumulate in tlie system, little by little, until at 
length the full effect of the poisons become manifested. Injurious con- 
sequences have been known to result from merely moistening wafers 
with the tongue ; now the ingredients used for coloring these include 



GUMS AND OII.S. 223 

many that are employed in sugar confectionery. How much more in- 
jurious, tlien, must the consumption of sugar thus painted prove when 
these pigments are actually received into the stomach." 

D.— Tlie Gums. 

407. Properties of the Gums. — The juices of many plants contain 
substances which ooze out through the bark, forming rounded trans- 
parent masses of gum^ as we often see upon cherry, plum, peach and 
apple trees. The gums differ considerably in properties. Cherry-tree 
gum is insoluble in cold water, but dissolves readily in boiling water, 
while gum-arabic dissolves in cold water, and gum-tragacanth dissolves 
in neither, but only swells up into a kind of mucilage. The solutions 
of gums are clear and tasteless, and have a glutinous and sticky nature, 
which adapts them for paste. 

408. Artificial Gum, — When common starch is heated to 300 degrees 
in an oven, or boiled in water made sour by a little sulphuric iicid, it 
is so altered as to dissolve in cold water, forming a clear, viscid solu- 
tion. The substance thus produced from the starch has the properties 
of gum, and is known as dextrine. 

409. How Gum is Composed. — In chemical composition, gum and 
dextrine do not differ from starch; they consist of 12 atoms of 
carbon combined with 10 of water. Gum exists in grains, and many 
vegetables, and hence is a widely-diffused element of food, although it 
does not occur in large quantities. Its dietetical value, as shown by 
its composition, is the same as starch and sugar, and hence it is 
grouped with the saccharine alimentary principle. 

£.— TSie Oils. 

410. Distinction between Volatile and Fixed Oils. — Oils are of two 

classes: 1st, those which, when smeared upon paper, produce a stain 
or grease spot, v/hich does not disappear by time or warmth, and 
hence called fixed oils; and, 2d, such as will vanish from paper, 
under such circumstances leaving no permanent stain, and there- 
fore called volatile oils. Tlie former is a universal and important 
element of diet, the latter presents itself chiefly among condiments, 
and will be there considered. 

411. Sources and Forms of Oily Bodies. — Oil is largely procured both 
from plants and animals, and from both sources it is chemically the 
Bame thing. It exists in many parts of vegetables, but is chiefly 
stored up in their seeds, from many of which it is obtained by pressure 



224 GENERAL PEOPERTIES OF ALIMENTARY SUBSTAKCES. 

in large quantities. In animal bodies it is deposited in the sacks or 
cavities of cellular tissue, and becomes accumulated in large quanti- 
ties in diflerent parts of the body. Oils and fats are chemically iden- 
tical, differing only in consistence^ and this quality depends upon tem- 
perature. Lowering the temperature of a liquid oil sufficiently, 
changes it to a solid, while raising that of a solid tallow converts it 
into a flowing oil. That which, in the hot climate of Africa, is liquid 
pahn oil, is with us solid palm lutter. Those oils, however, which at 
ordinary temperatures are not perfectly fluid, but have what is called 
an oily consistence, become much thinner a-cd completely liquid when 
heated. 

412. Proportion of Oil ia Articles of Diet. — The proportion of oily 
matter from many sources is variable, as in the case of meat, which 
may more or less abound in fat. Nor has its amount in many vege- 
tables been determined with suflicient certainty. The following are 
the quantities given by the later authorities : 

Tolk of Egg 28-75 per cent 

Ordinary Meat (Liebig) 14-03 " 

Indian Corn 9- " 

Oatmeal (husk excluded) 6- " 

Cow's Milk 8-13 " 

Eye Flour 3-5 " 

WheatFiour lto2 " 

Barley Meal 2- " 

Potatoes (dried) 1- " 

Eice -8 " 

Buckwheat -4 " 

il3. Its Composition. — Oleaginous bodies are distinguished from 
all the other alimentary principles, by their chemical composition, and 
the resulting properties. They resemble the preceding substances 
which we have been considering in containing three elements, carbon, 
hydrogen and oxygen ; but they differ from all of them in this im- 
portant respect, that they are composed almost entirely of hydrogen 
and carbon, with but a small proportion of oxygen. The composition 
of hogs-lard, as given by CnEVEEUL, may be taken as an example of 
the general structure of this alimentary group. It consists of carbon 
79, hydrogen 11, oxygen 10 parts in a hundred. "We have seen that 
hydrogen and carbon are the active fire-producing elements of fuel 
(80). As the oils are so rich in these, they rank high as combus- 
tibles, burning with great intensity, and yielding much heat. It has 
been also noticed that oils may be decomposed into several acid and 
basic principles (195). 



THE ACIDS FOUND IN FEUXTS. 225 

F.— Tlie Veg-etable Acids. 

414. Combinatioa and Composition. — The sourness of fruits and suc- 
culent vegetables is due to various acids produced in tlie plant, and 
which they contain usually in quite small proportions. They exist in 
two states : 1st, as pure acids, or free, when they are strongest ; and, 
2d, combined with bases, as potash, lime, &c., by which they are 
partially neutralized, and thus rendered less pungent to the taste. In 
this case they exist as acid salts (691). The vegetable acid group con- 
sists of but three elements, carbon, oxygen, and hyarogen, like the 
starch and oil groups, but it is distinguishable from tnem by contain- 
ing but a small share of hydrogen and a large proportion of oxygen. 
The composition of the different vegetable acids is quite variable, but 
they all agree in possessing less hydi-ogen and more oxygen than any 
other class of organic alimentary principles. Their nutritive value is 
very low. 

415. Acid of Apples — Malic-Acid. — This is the peculiar acid of apples, 
and it is also found in numerous other fruits. Thus, it exists free in 
pears, quinces, plums, peaches, cherries, gooseberries, currants, straw- 
berries, raspberries, blaokberries, elderberries, pineapples, grapes, 
tomatoes, and several other fruits. It exists veiy abundantly in green 
apples, causing their extreme acidity, and diminishes as they ripen. 
The wild crab-apple is much richer in malic-acid than the cultivated 
fruit, and generally speaking, in proportion as we obtain sweetness by 
culture, we deprive the apple of its malic-acid. No use is made of 
this acid in the separate state. 

416. Acid of Lemons — Citric-Acid — Gives their sourness to the lemon, 
orange, citron, and cranberry. Mixed with malic-acid, it exists also 
in the gooseberry, red-currant, strawberry, raspberry, and cherry. 
Citric-acid is separated from lemon juice, and sold in the form of crys- 
tals, which may be at any time redissolved in water, and by flavoring 
with a little essence of lemon, an artificial lemon juice is produced, 
which is used like the natural juice in the preparation of refreshing 
and cooling beverages. 

417. Acid of Grapes — Tartaric-Acid. — This acid in the free state ex- 
ists in the grape, and is found besides in some other fruits. It also 

' exists abundantly in the grape in combination with potash, as acid, 
tartrate of potash, or cream-of-tartar. Tartaric-acid is prepared and 
sold in the crystalline form as a cheap substitute for citric-acid, or 
lemon juice. It does not absorb moisture when exposed to the air 
like citric-acid, but is inferior to it in flavor. The commercial eflfer- 

10* 



226 GENERAL PEOPERTEES OF AUMENTAKT SUBSTANCES. 

vescing, or soda powders, consist of 30 grains of bicarbonate of soda, 
contained in a blue paper, and 25 gi*ains of tartaric acid, in a white 
paper, to be dissolved in half a pint of water. 

418. Oxalic-Acid — Exists in sorrel, and also in the garden rhubarb 
or pie-plant, combined with and partially neutralized by potash or 
lime. It is a prompt and mortal poison when pure, and fatal results 
frequently occur from mistaking its crystals for those of Epsom salts, 
which they much resemble. 

419. Vegetable Jelly, Pectine or Pectic-Acid. — This is obtained from 
the juice of apples, pears, quinces, currants, raspberries, and many 
other fruits ; also, from turnips, carrots, beets, and other roots. It is 
composed similarly to the vegetable acids, having an excess of oxygen. 
Vegetable jelly is thought not to exist exactly as stick in the plant- 
juices, but to be produced from another substance in the process of its 
separation. The substance from which it is obtained is soluble in the 
vegetable juices, but the jelly itself is scarcely soluble in cold water. 
Boiling water dissolves it, but it coagulates again as the water cools. 
It is commonly prepared by mixing sugar with the juice, and suffering 
it to stand for some time in the sun, by which a portion of the water 
is evaporated ; or it may be boiled a short time. But when long 
boiled, it loses the property of gelatinizing by cooling, and becomes of 
a mucilaginous or gummy nature. This is the reason that in making 
cuiTant or any other vegetable jelly, when the quantity of sugar is not 
sufficient to absorb all the water, and consequently it becomes neces- 
sary to concentrate the liquor by long boiling, the mixture often loses 
its peculiar gelatinous properties, and the jelly is of course spo'^ed. 
It differs from animal jelly in containing no nitrogen, and although 
readily digestible, it is supposed to be but slightly nutritive. Isinglass 
is often added to promote the stiffening of vegetable jellies, and sugar 
also has a similar effect. They form cooling and agreeable articles of 
diet for those sick with fevers and inflammatory complaints. Jams 
consist of vegetable pulps preserved with sugar. They are very simi- 
lar in their uses and effects to the fruit-jellies, from which they prin- 
cipally differ in containing a quantity of insoluble, and therefore indi- 
gestible ligneous matter (or vegetable membranes, cellular-tissue and 
sometimes seeds), w^hich in the healihy state of the system contribute, 
by their mechanical stimulus to promote the action of the bowels, but 
in irritable conditions of the alimentary canal, sometimes prove injuri- 
ous. (Peeeie A .) 

420. Acetic Acid, oy Viucgar. — The acid in most general use for diet- 
etical purposes is the acetic, or acid of vinegar, which we obtain by 



THE ALBUMINOUS PRINCIPLES. 227 

fermentation (491). Good strong vinegar contains about four per cent. 
of the pure acid. Vinegar may be easily made at any time by adding 
ferment, or yeast, to water sweetened with sugar or molasses, or any 
sweet vegetable juice, and exposing the whole for a reasonable time to 
the air in a warm place. Vinegar itself added to the mixture will act 
in the way of yeast to start the operation. There accumulates in old 
vinegar a thick, ropy matter, called viother^ because it is capable of 
producing the acetous change in a sugary solution. It consists, like 
yeast, of vegetable cells (496). The juices of most fruits contain all 
the elements necessary for fermentation and souring. Apple and grape 
juice, at first, undergo the vinous change producing cider and wine, and 
the process continued converts them both into vinegar {cider-vinegar 
and wine-vinegar), which are prized, on account of the fruity aroma 
which accompanies them. 

2. — Peinoiples CoNTAININa NlTEOaEiSr. 
A.— Vegetable and Animal Albumen. 

421. !t exists in both organized Kingdoms." — We are aU familiar with 
albumen or white of eggs, and recollect the remarkable cliange it un- 
dergoes by heat, being coagulated or altered from a transparent liquid 
to an opaque, white, brittle solid. This substance exists in small pro- 
portions dissolved in the juices of plants. If such juices are clarified 
and then boiled, the albumen coagulates in thin flakes, and may be 
separated from the liquid. The same substance exists also in small 
quantities, laid up dry and solid in seeds and grains, but its exact pro- 
portion in various parts of plants has not been ascertained. Albumen 
exists also in animals, and is a much more abundant constituent of 
these than of plants. It constitutes, according to Regnault, about 19 
per cent, of healthy human blood, and is therefore found in large 
quantities in all parts of the system. It exists in the peculiar animal 
juices, in the glands, nerves, brain, and around the muscular fibres of 
flesh. 

422. Composition of Albumen. — In composition, albumen differs widely 
from the aliments we have considered ; it contains not only the aU- 
ments they contain — carbon, oxygen, and hydrogen,- —but in addition, 
a large proportion of nitrogen, and also a minute amount of sulphur. 
The chemical structure is thus complex. The result of the latest 
analysis is, that a compound atom of albumen consists of 216 carbon, 
189 of hydrogen, 68 "of oxygen, 27 of nitrogen, and 2 of sulphur. 
The albumen of eggs, however, contains a slightly larger proportion 



228 GEIfEEAL PKOPEETIES OF ALIMENTABT SUBSTANCES. 

of sulphur. Vegetable and animal albumen are essentially the same 
thing in properties and composition, differing no more upon analysis 
than two samples from the same source. 

423. General Properties of Albamen. — It exists in two states — soluble 
and insoluble, or coagulated. The coagulation is eflfected by simple 
heat ; but there is much confusion of statement among different writers 
as to the point of temperature at which it solidifies. This depends 
upon cii'cumstances. A moderately strong solution of pure albumen 
in water becomes turbid at 140°, and completely insoluble at 145°, and 
separates in flakes at 167°. "When excessively diluted, no turbidity 
can be produced by a less heat than 194°, and it will only separate in 
solid masses after it has been boiled a considerable time. As a general 
rule, albumen coagulates with greater difficulty in proportion to the 
quantity of water in which it is dissolved. Coagulated albumen 
refuses to dissolve in cold water, merely swelling up in it. There are 
many substances which, if mixed with it, coagulate albumen when 
cold, as alcohol and corrosive sublimate, the mineral acids, and many 
salts, while the presence of alkalies hinders its coagulation. The 
change of coagulation does hot alter or disturb its composition. 

IS.— Veg:cta1>le and Animal Casein« 

424. Source and Composition. — The water in which flour has bee» 
washed or difi'used, as in separating starch, contains a small portion 
of a dissolved substance, which is coagulated by the addition of an 
acid, and may be then separated. It is called vegetable casein, and is 
found in the largest proportion in peas and beans, constituting from 
20 to 28 per cent, of their weight. This substance is identical in 
properties with the curd of milk, which is known as animal casein, 
and is the chief ingredient of cheese. The identity of vegetable anu 
animal casein is well illustrated by the fact that the Chinese make a 
real cheese from peas. They are boiled to a thin paste, passed through 
a sieve, and coagulated by a solution of gypsum. The curd is treated 
like that formed in milk by rennet. The solid part is pressed out, 
salted, and wi'ought into cheese in moulds. This cheese gradually 
acquires the smell and taste of milk cheese ; and when fresh, is a 
favorite article of food with the people. The composition of vegeta- 
ble and animal casein is nearly if not qiiite identical with that of 
albumen (422). 

C— Vegetable and Animal Fibrin. 

425. The Blood and Vegetable Juices.— When blood is drawn from 



FIBRIN AND GLUTKN". 



229 



Fig. 91. 




Fibres of lean meat magnifled. 



the living body, in a short time it clots ; that is, a net-Avorlc of fibres is 
formed within it. These fibres consist of animal fibrin^ which was 
dissolved in the blood, and then took on the solid form {spontaneom 
coagidation). Vegetable juices, as those expressed from turnips, car- 
rots, beets, &c., also contain the same kind of matter which they deposit 
on standing, that is, it sj^ontaneously coagulates^ and this is known 
as vegetable fibrin. If a piece of 
lean beef be long washed in clean 
water, its red color, which is due to 
blood, gradually disappears, and a 
mass of white fibrous tissue re- 
mains, which is known as animal 
fibrin. The accompanying diagram 
(Fig. 91) shows its structure as seen 
under the microscope. The paral- 
lel fibres have cross markings, wrinkles, or striee. By the contraction 
of a muscle in the living animal the striae are made to approach each 
other, become less distinct, and the fibre increases considerably in 
breadth and thickness. 

426. Gluten. — If wheat flour be made into a dough, and then 
kneaded on a sieve or piece of muslin under a stream of water 
(Fig. 92), its starch is 
washed away, and there 
remains a gray, elastic, 
tough siibstance, almost 
resembling a piece of ani- 
mal skin in appearance. 
"When dried it has a glue- 
like aspect, and hence its 
name, gluten. When thus 
produced, it consists chiefly 
of vegetable fibrin ; but it 
contains also a little oil, 
with albumen and casein. 
That from other grains is 
different in the proportion _ 
of these constituents ; rye "• 
gluten, for example, con- 
sists largely of casein, and has less of the tenacious fibrinous princi- 
ple. By acting upon crude gluten with different solvent agents, it 
is separated into four principles as follows : 



Fig. 92. 




230 GENERAL fKOPERTIES OF ALIMEXTARY SUBSTANCES. 

Vegetable fibrin • 72 per conU 

Gluten 20 " 

Casein (mucine) 4 " 

Oil 3-7 " 

Starch (accidental), small quantity 

Total 99-7 " 

427. Animal Fibrin. — The muscles or lean meat of animals are prin- 
cipally comijosed of this substance, its proportionate quantity being 
greatest in llesli that is dark-colored, and belongs to animals that have 
attained their full growth. Its characters vary somewhat in different 
animals, and in the same animal at different ages. Its color is vari- 
able ; in beef and mutton it is red ; in pigeons and many kinds of 
game it is brownish ; pink in veal, salmon color in pork ; in fish, white 
or semi-transparent, though all animals yield it on various colors. 
When washed free from blood and other foreign substances, pure 
fibrin is white and opaque, but darkens by drying. 

428. Properties of the Kltrogenous Principles. — "Whatever their form or 
source, these substances are identical in composition, a fact of great 
importance in connection with animal nutrition. They present varia- 
tions of aspect and physical properties, and different solubilities, albu- 
men and casein being soluble in water, while the others are not ; and 
while fibrin coagulates or solidifies spontaneously, albumen is altered 
in the same manner by heat, and casein by acids. It is possible tliat 
some of these conditions may be influenced by the mineral i)hosphate3 
which these substances contain in variable amount, but this point is 
not yet determined. These substances are decomposed by heat, and 
exhale a pungent odor like that of burnt feathers. They may be long 
preserved when dried, or even in the moist state when cut off from 
the atmosphere ; but in contact with air and moisture they quickly 
decompose, putrefy, and call into existence a host of microscopic ani- 
malculas. We shall consider these substances again (678). 

D.— Gelatin. 

429. Its Sonrccs, Properties and Uses. — There exists in the bone, carti- 
lages and various membranes of animal bodies, a principle rich in ni- 
trogen, called gelatin. It is not identical in composition with the ni- 
trogenous class which we have been considering, nor is it like them 
produced in the vegetable kingdom ; but it is supposed to be derived 
from them in the animal system. It dissolves in hot water, and when 
cooled, forms a white jelly. It is tlie universal principle of animal 
jellies. Common glue consists of gelatin, but in this form it is not 



DIFFERENT NAMES OF THE NITROGENOUS PRINCIPLES. 231 

nsed dietetically. Isinglass is a preparation of gelatin in various forms 
to be used as food. It is mainly procured from the air-bag or bladder 
of fishes. Four parts of isinglass convert 100 of water into a trem- 
bling jelly. Gelatin is also extracted from calves' feet, in forming calves 
footjellij^ and calves' heads are also employed to furnish jelly in mak- 
ing mocTc turtle soup. Gelatin is used not only to produce jellies, but 
to thicken and enrich gravies and sauces, and also as a clarifying or 
' fining ' agent to clear coifee or other mixtures. 

430. Differeut Names applied to these Sabstauces. — The recent rapid 
progress of organic chemistry, has brought this class of substances for- 
ward into new and highly interesting dietetical relations, and there 
has been a confusion in the terms applied to them, which, though 
perhaps inevitable, is at first very embarrassing to unscientific readers. 
As they all contain nitrogen^ they are called nitrogenous alimentary 
principles ; and as one of the names of nitrogen is azote^ they are call- 
ed azotized compounds. As they have all (except gelatin) the same 
composition as albumen^ and are convertible into it, they are often 
called albuminous substances. As they form the material from which 
the body is nourished and built up, Liebig named them plastic ele- 
ments of nutrition ; they are also called nutritive principles, the_;?esA- 
forming and blood-malcing substances. Muldee supposed that a com- 
mon principle could be separated from all of them by getting rid of 
sulphur, (of which they contain variable traces,) and he called this 
principle pirotein^ and hence the group has been called protein or pro- 
tcinaceous compounds. Mtilder's peculiar views are abandoned, but 
his terms are still in current use. 

3. Compound Aliments. — ^Vegetable Foods. 

431. Our common articles of diet consist of the alimentary princi- 
ples which have just been noticed, combined together and forming 
what are known as compound aliments. They are naturally divided 
into vegetable foods and animal foods ; of the former first. 

A.— Tbe Grains. 

432. Composition of Wheat. — We begin with wheat, the prince of 
grains. It consists of gluten, starch, sugar, gum, oil, husk, and water, 
with salts that are left as ash when it is burned. It is maintained by 
some that there is really no sugar present in the ripe grain, especially 
in wheat, but that it is produced by the action of air and water upon 
the starch during the process of bread making, or analysis. The 
proportion of constituents in wheat is liable to considerable variation, 



232 GE^TERAL PROPERTIES OF ALIMENTARY SUBSTANCES. 



from many causes, as variety of seed, climate, soil, kind of fertilizer!^ 
seed, time of harvest, &c, "We give five analyses. 



"Water 


Vauquelin. 


DtTMAS. 


Bbck. 


Flinty 
Wheat. 

12-00 

14-60 

56-50 

8-50 

4-90 

2-30 


Soft 
Wheat. 

10-00 

12-00 

62 00 

Y-40 

5-SO 

1-20 


Flinty 
Wheat. 


Soft 
Wheat. 


Genesee 
Wheat. 


12-00 

14-55 

56-50 

8-48 

4-90 

2-30 


10-00 
12-00 
62-00 
7-36 
5-Sl 
1-29 


12-40 
11-46 
TO-20 

[5-20 












Total 


98-80 


98-40 


98-73 


98-46 


99-26 



433. Proportion of Gluten in Wheat. — It will be shown when we come 
to speak of the physiological influence of foods, that the most valuable 
portion, the strictly nutritious part, is that containing nitrogen, and 
that therefore 'gluten,' the properties of which have betn noticed 
(426), is of the first importance in examining the grains. From an 
analysis of six samples of wheat, made by Vauquelin, we get an aver- 
age of 11-18 per cent, of gluten ; Dumas, from three samples obtain- 
ed an average of 12-50 per cent. ; and Dr. Lewis 0. Beok, who made 
an investigation of the subject, at the direction of the Federal Govern- 
ment, and of 33 samples of wheat, gathered from all parts of the coun- 
try, procured an average of 11-72 per cent, of this constituent, the 
specimens ranging from 9-85 to 15*25 per cent. The mode of exam- 
ination, however, adopted by Dr. Beck — that of washing away the 
starch by a stream of water (426) — is not the most accurate. A por- 
tion of albumen and casein, with small particles of gluten, are carried 
away by the stream — which would make the remaining quantity an 
undei'-statement of the true proportion of nitrogenous matter. This 
loss is as.sumed to be compensated for by the oil retained in the gluten, 
and the result is thus to a certain degree guessed at. Horsfoed pro- 
ceeded more accurately, by making an ultimate analysis of the wheat, 
and calculating the amount of nitrogenous matter by the quantity of 
nitrogen finally obtained. Six samples of wheat thus treated, yielded 
15-14 per cent, of gluten. Quantities of gluten are mentioned by 
Davt and Botissingalt as high as 20 or 30, and even 35 per cent., but 
these are probably erroneous over-statements. For general purposes 
we may adopt Dr. Beck's results — 11-72 of gluten, or in even num- 
bers 12 per cent. 

434, Quality of the Gluten of Wheat.-^But not only do wheats diffei 
in the proportion of gluten, but also in its quality. In some it is more 
Wugh and fibrous, or ' sounder ' and ' stronger, ' than in others. 



THE GLUTEN AND WATER OF WHEAT. 233 

Moreover, any injury or damage that flour may sustain, is most 
promptly manifested by a change in tlie gluten ; it is both reduced in 
quantity and diminished in tenacity. Flour dealers and bakers deter- 
mine the quality of flours by making a few grains into a paste with 
water, when its value is judged of by the tenacity of the dough, the 
length to which it may be drawn into a thread, or the extent to which 
it may be spread out into a thin sheet. M. Boland has invented an 
instrument for determining the quality of gluten. A little cup-shaped 
copper vessel, which will contain about 210 grains of fresh gluten, is 
. secured to a copper cylinder of three-fourths inch diameter and six 
inches long. It is then heated to about 420° in an oil bath. The 
gluten swells, and according to its rise in the tube so is its quality. 
Good flours furnish a gluten which will augment to four or five times 
its original bulk, while bad flours yield a gluten which does not swell, 
but becomes viscous and nearly fluid, adhering to the sides of the tube, 
and giving off occasionally a disagreeable odor, whilst that of good 
flour merely suggests the smell of hot bread. — (Mitchell.) 

435. Macaroni and Vermicelli are pastes formed from wheaten flour, 
and made to take various shapes by being passed through holes in me- 
tallic plates. Those flours are best adapted for this preparation which 
make the toughest paste ; those, therefore, which are richest in gluten, 
and where this element is of the best quality. The wheat of southern 
or Avarm climates is said to abound most in gluten, and hence to be 
better fitted for this production. Our chief supplies of macaroni are 
from Italy. The English have attempted the manufacture by separat- 
ing the gluten of one flour and incorporating it into another. Their 
success has been but indifferent, nor have we succeeded satisfactorily 
■with it in this country. The best macaroni should retain its form, and 
only swell after long boiling, without either running into a mass or 
falling to pieces. 

436. Water in Wheat. — The wheat grain consists of a solidified veg- 
etable milk. As the grain ripens, evaporation of water takes place, 
and the milk condenses into a hard mass. Wheat ripened under the 
hot sun of this dry climate evaporates much of its water, and dries 
harder, with a tendency to shrivel in the berry ; Avhile in the cooler 
and damper climate of England longer time is allowed for ripening, 
and evaporation is slower, so that the same variety of English wheat 
presents a larger and plumper berry than if grown in this country. 
Dr. Beck's examination gave an average of 12-78 per cent, of water, 
the range being from 11-76 to 14-05. Different wheats, however, are 
stated to vary in their natural proportion of water so widely as from 
5 to 20 per cent. 



234 GENERAL PROPERTIES OF ALIMENTARY SUBSTANCES. 

437. Grinding of Grain. — Grain is converted into flour by being 
ground between two horizontal stones, the upper of which revolves, 
while the lower is stationary. The mill-stones (buhr-stones) are com- 
posed'of a peculiar hard and porous sand-stone, so that the working 
Burfoces consist of an infinite number of minute cutting edges. There 
is an opening in the centre of the upper revolving stone through 
which the grains are dropped. Tlie lower stone is convex and the 
upper one is concave, so as to match it ; but they do not perfectly 
ioiu or fit. From the centre outwards, they approach closer together, 
so that the grain is first coarsely crushed, and then cut finer and f ner 
as it is carried to the circumference by the centre-flying (centrifugal) 
force. The crushed grain, as it leaves the stones,. is not an absolutely 
uniform powder, composed of equal sized particles, but consists of 
parts which have been difterently afl:ected by the grinding pi-ocess. 
Some are coarser, and others finer, so that it becomes possible to 
separate them. The gi'ound mass is therefore conveyed away and 
bolted; that is, passed through a succession of sieves, and separated 
into several parts, fine flour, coarse flour, bran, &c, 

438. Structnre of the Grains. — When we consider wheat or other grain 
with reference to its grinding and sifting capabilities, the proportion 
and quality of its separated products, several things require notice in 
regard to the structure of the kernel or berry. Each grain consists of 
a farinaceous body, enclosed in a membranous husk or skin. This 
husky envelope varies in properties ; in some wheat it is thin, smooth, 
and translucent ; in others, rough, thick, and opaque ; in some light- 
colored, in others dark ; in some tough, in others brittle ; and in some 
it peels or flakes off readily under the stones, and in others it is very 
adherent to the kernel. The other elements of the seed, albumen, glu- 
ten, starch, and oil, and the salts which it leaves as ash when burned 
(446), are not equally distributed throughout its mass. Immediately 
beneath the incrusting husk, is a layer of matter of rather a darkish 
color, and not very easily reduced to an impalpable powder. It is 
rich in gluten, and contains oil, which exists in minute drops enclosed 
in cells. Underneath this is the heart of the seed, which is whiter 
and more readily crumbles to a fine dust. This part consists more 
purely of starch, and forms the finest and 'whitest flour. There is 
a certain degree of interdiffusion of these elements throughout the 
body of the seed, yet, upon dissection, they are each found in excess 
in the parts indicated. 

439. Aniitomy of Grains Illustrated. — An idea maybe gathered of this 
distribution of substances throughout the cereal seeds, ])y the accom- 



STEUCTUBE OP THE CEEEAL GRAINS. 



235 



panying section of a grain of rye highly f a 9% 

magnified (Fig 93) : a represents the outer -_. :^-^'-^-_.. 

investing seed-coat, consisting of three 5=5^^1^;^— ^crcz^cr' ':r, 
rows of cells ; i, an inner membrane or X / : f> 

seed-coat, composed of a single layer of '"" rs:^''5^---'r^f'' 

cells; c, a layer of cells containing gluten. ' , ■ :}}^^J^^^/^0 
These three form the bran ; d, cells con- iki%f^^M^^^^^l(^ 
taining starch grains in the interior of ^^^^li^s^f^i^^Sr^^ 
the seed. Fig. 94 represents a cell con- 
taining starch, more highly magnified, and Fig. 95, the appearance of 
the grains of rye starch viewed by a still stronger power. 

440. Parts Separable by Sifting. — These several portions oppose un- 
equal resistance to the pulverizing force of the mill- 
stones. The outer fibrous portion which forms the bulk 
of bran is least aifected ; the tough coherent gluten is ^'.>,sj^> 
divided still finer, while the brittle starch, of which the ^pMvv 
grain is mainly composed, is crushed most completely. |'i^-^^||^^ 
As the particles of these substances, therefore, are of \k^i 
difierent sizes, they may be separated by a bolting cloth, ■'^"' 
having different degrees of fineness of texture. The 
product is divided by the miUer according to custom or 
fancy, four or five grades being often established, which, of course, 
vary much in composition and properties. 

441. Properties and Composition of Bran. — From what has been said 
of the husk, it will appear that the quantity of bran yielded by differ- 
ent wheats, is liable to variation (438). As the 

. Fio. 95. 

husk is detached with different degrees of ease, it 

is evident that it may carry with it more or less 

adherent matter of the grain, by which its com- ,' ,';^y\ \ ^[(^Q)] 

position will be made to fluctuate. Johnston ^ ^' " 

states, that in good wheat the husky portion 

amounts to between 14 and 16 per cent, of its vc^l^m 

whole weight. The same authority found six 

wheats to yield bran of an average composition, 

as follows : 

Water 131 

Nitrogenlzed matter 19-3 

Oil 4-7 

Husk, and a little starch 55'6 

Saline matter (ash) 7-8 

100 





236 GENERAL PEOPEETTES OF ALIMENTAET SUBSTANCES. 

This discloses the nitrogenous matter, the oil, and the salts, in larger 
proportion than they exist in the interior of the seed. The excess 
of oil existing in the husks of wheat, helps to protect it against the 
penetration of moisture, and enables it to be washed (which ought al- 
ways to be done before grinding), without wetting the inner part of 
the grain. 

442. White and dark-colored Flours. — In separating flour into dif- 
ferent grades, the finest and whitest will contain the largest quantity 
of starch, while the coarser will more abound in gluten, and present 
a darker color. From the soft wheats the bran peels off readily under 
the stones, and separates perfectly in bolting; and as these varie- 
ties contain least gluten, they yield the whitest or superfine flours. 
But the outer coating clings so closely to the hard or flinty sorts, that 
much of it is ground up finely with the flour, imparting to it a dark 
color, an effect which is also heightened by the larger proportion of 
gluten existing in the harder kinds. It is thus apparent that white- 
ness is not an indication of nutritive value of flour, but rather the 
reverse. We may add here, that flour of the first quality holds 
together in a mass when squeezed by the hand, and shows impressions 
of the fingers and even the marks of the skin mncTi longer than when 
it is of inferior grade. The dough made with it is gluey, ductile, 
and elastic, easy to be kneaded, and which may be draAvn out into 
long strips, or thinly flattened without breaking. 

443. Loss of Weight by Eraporatioii. — When wheat is kept for several 
months, it loses water by evaporation, becomes denser, and one or 
two pounds a bushel heavier. When ground it gets hot, and still 
more of its moisture is evaporated, so that the flour and brai\ 
although twice as bulky as the wheat, weigh some two or three per 
cent. less. 

444. Injarions changes in Flonr. — Wheaten flour becomes whiter 
with age, but it is at the expense of gradual deterioration of flavor, 
sweetness, and nutritive quality. Bergs kept various samples of 
flour, and found that the second and third qualities, which contained 
most gluten^ were completely spoiled, after keeping only nine months, 
though preserved in casks in a cool, airy, and dry warehouse. Mit- 
CHEELicn and Keockee showed that wheat in which sugar was proved 
to be absent before sending it to the mill, yielded, after being ground, 
i per cent, of it. Starch was thus transformed into sugar, which coidd 
not be done otherwise than through the internal action of the gluten 
aided by air and superabundant moisture (473). The mutual action 
of the gluten, and the natural moisture of the flour, seem often capa- 



THE GRAINS — WHEAT. 231 

ble, at common temperatures, of slowly bringing about tbis injurious 
cbange. But when the flour comes out hot from the friction of the 
stones, and is left to cool gradually in large heaps, decomposition quickly 
sets in, starch is changed to sugar, and perhaps sugar to alcohol, and 
even alcohol to vinegar ; so that the process advances rapidly to the 
souring stage. This action always takes place in the middle of the 
heap first, and proceeds towards the surface, the air enveloped in 
the flour, and the heat produced by chemical action, favoring the 
change most in the centre. Flour, as soon as ground, should therefore 
be conveyed to properly- constructed chambers, and quickly cooled, or 
if it be desired to preserve it for some time, it should be dried at a 
low heat. The amount of damaged flour thrown into the market is 
immense. Large quantities of it are due to careless and imperfect 
cooling, by which chemical changes are commenced, which time con- 
tinues. Sometimes, to separate the bran most perfectly and procure 
the whitest flour, the miller moistens the grain previously to grinding ; 
but if such flour is packed in barrels or sacks without artificial drying, 
it rapidly moulds and sours. From these considerations, we infer 
the desirableness of procuring flour for household use, freshly ground, 
and frequently from the mill, where that is practicable. 

445. Farina. — A wheaten preparation under this name has come 
recently into general use, the same formerly known as 'pearled 
wheat.' It consists of the inner portion of the kernel of the finest 
wheat, freed from bran and crushed into grains, (granulated,) the fine 
floury dust and smaller particles being all removed. In cooking, it 
absorbs much water or milk, and forms an easily-digestible prepara- 
tion, readily permeable by the juices of the stomach. In consequence 
of containing nitrogenous matter, it is greatly superior in nutritive 
power to cornstarch, arrowroot, tapioca, as a diet for invalids and 
children (746). Prof. J. 0. Booth of Philadelphia, analyzed Ilecker's 
Farma with the following results: Starch 60-4, nitrogenous matter 
11-6, gum 2-9, sugar 2-41, bran 2-1, water 9-9. Professor Booth re- 
marks: " The analysis is sufiicient to show the excellent qualities of 
the farina, whether as a simple diet for invalids, or as an excellent 
food for the healthy." 

446. What Dlinerals exist ia Wheat. — When wheat is burned, there 
is left about 2 per cent, of ash, which consists of various mineral in- 
gredients. An average of 32 of the most recent and reliable analyses 
gives the leading constituents, as follows: Phosphoric acid 46 per 
cent., (nearly half its weight,) potash 29-97, soda 3-30, magnesia 3'35, 
sulphuric acid -33, oxide of iron -79, and common salt -09. Phos- 



238 GENERAL PROPEKTIES OP ALIMENTARY SUBSTANCES. 

phoric acid is the characteristic and predominant element, potash and 
magnesia occurring next in tlie order of quantity. These mineral sub- 
stances are unequally diffused throughout the seed. Johnston has 
shown by an analysis of six samples of wheat, the ground product of 
which was divided into four qualities, that the mineral substances are 
distributed as follows. "We give the average: — fine flour 1-08 per cent 
next grade 3-8, coarser still 5*2, bran 7"2. The ash of bran contains 
considerable silica. The presence of these mineral substances is far 
from accidental, as was foi'merly supposed ; we shall point out some 
of their important uses in the system when considering the physio- 
logical effects of food (690). 

4i7. Properties and Composition of Rye. — This grain ranks next to 
wheat in bread-making and nutritive qualities. It produces a larger pro- 
portion of bran than wheat, yielding less tiour, and that of a decidedly 
darker color. It contains more sugar than wheat, which accounts for 
the sweet taste which is peculiar to new rye-bread. Its husk has an 
aromatic and slightly acidulous flavor, which renders it agreeable to the 
palate. The«. bran should not, therefore, be entirely separated from 
the flour; for if the grain be ground fine and divested entirely of the 
husk, the bread will be deprived of much of its pleasant taste. The 
gluten of rye flour, although sufficiently tenacious to make good bread, 
is less tough and fibrous than that of wheat. Indeed it is more prop- 
erly a kind of casein (424), or 'soluble gluten,' for when rye dough 
is washed with water, instead of remaining together in an adherent 
mass, its gluten diffuses itself throughout the liquid. Eye is generally 
stated to be less rich in the nutritive nitrogenous constituents than 
wheat. It has not been so thoroughly examined as that grain, but the 
analyses that have been made would seem to show that it is very 
little, if at all, inferior to it in nutritive power. Boxjssingault obtain- 
ed from the grain of rye 24 per cent, of bran, and 76 of flour. He 
separated by drying 17 per cent, of moisture, and the dry flour gave of 

Rye (Bocssisgault). Rye (Poggaile). 

Gluten, albumen, &c 10-5 Nitrogenous matters 8-790 

Starch W'O Starch and dextrin 65-533 

Gum 11-0 Fatty matters 1-992 ' 

Fatty matter 8-5 Lignin 6-8S3 

Sugar 3-0 Mineral matters 1-772 

Epidermis and salts C'O Water 15-530 

Loss 2-0 

A sample of rye dried in Prof. JonNBTON's laboratory, lost 14'50 per 
cent, of water. IIoesfoed examined four samples of European rye, 



THE GRAINS — INDIAN CORN — OATS. 239 

and obtained an average of 14 per cent, of water, and 13'79 per cent, 
nitrogenous compounds. 

4^8. Indian Corn or Maize. — This grain is distinguished cliemically by- 
containing a larger proportion of oily or fatty matter than any other. 
It is quite rich in nitrogenous constituents, though less so than wheat. 
Its pecuhar protein element takes the name of sein (from zea maize, 
the botanic name of Indian corn) ; it is not of a glutinous, adhesive 
nature, and hence maize flour or meal will not make a dough, or fer- 
mented bread. It is prepared in several forms. Its composition is 
given as follows : 

Maize (Payen). Yellow Maiie (Poggaile). 

Starch 67-55 Nitrogenous matters 9-905 

Gluten or zea 12-50 Starch, dextrin, sugar (>4-535 

Dextrin or gum 4-00 Fatty matter 6-GSO 

Fatty matter 8'SO Lignin and coloring matter 3-963 

Celulose 5-90 Mineral 1-410 

Saltsorashes 1-25 Water 13-472 



10000 



HoESFOED obtained 13'65 of nitrogenous matter from maize meal, and 
14*66 from maize grain. Samp is Indian corn divested of its outside 
skin or bran, and of its germinal eye, the grain being left whole or 
nearly so. In hominy each grain is broken up into a number of small- 
er pieces. The meal of Indian corn, in consequence of its excess of 
oily matter, attracts much oxygen from the air, and is hence very 
prone to change, and does not keep well. This is the serious draw- 
back of this most valuable grain ; though cheap, nutritive and health- 
ful, it is difficult to transport and preserve its meal, especially in warm 
seasons or climates. 

449. Oats. — This grain is not employed to any considerable extent 
as an article of diet for man, in this country. The oat varies greatly 
in weight, ranging from 30 to 40 lbs. per bushel. In grinding, 30 lbs. 
give 16 of meal and 14 of husk, while a bushel weighing 40 lbs. yields 
23 lbs. 6 oz. of meal and IG lbs. 10 oz. of husk — the largest proportion 
of bran yielded by any grain, yet different varieties give different re- 
sults. Oat flour stands before all other grains in point of nutritive or 
flesh-producing power, beinji; first in its proportion of the nitrogen- 
ous element. It is also distinguished by its large quantity of fat or 
oil, ranging in this particular next to Indian corn. The following 
table gives the result of an analysis of French oats, by Boussinoault, 
and the average of four samples of Scotch oats, by Prof. Norton. 



240 GENERAL PROPERTIES OP ALIMENTARY SUBSTANCES. 



(Bou«singault). (NoKTO!"). 

starch 461 Starch 65-10 

Sugar 60 Sugar 2-49 

Gum 33 Gum 2-22 

Oil 6T Oil 6-55 

Avenin.. j Avenin 16-50 

Albumen I 13-T Albumen, 1-42 

Gluten . . ) Gluten 1-67 

Husk, ash, and loss 23-7 Epidermis 2-17 

Alkaline, salt, and loss 1-84 



100-0 



99-96 



Norton's analysis, the most accurate we have, thus gives 19*59 per 
cent of nitrogenous compounds. Again, from nine samples of dry 
oats ne obtained 16"96 per cent, of protein compounds, the specimens 
ranging, from 14 to 22 per cent. Prof. Hoesfoed obtained from three 
samples <iu average of 12-83 per cent, water, and 16*59 protein con- 
stituents. From the dried grain he got 21 5 per cent, of these com- 
pounds, if oatmeal be mixed with water, it does not form a dough 
like wheat fiour, and if it be washed upon a sieve, nearly the whole 
will be carried through, only the coarse parts of the meal remaining 
behind. The chief portion of the nitrogenized matter of the oat re- 
sembles casein more than gluten, and has received the name of avenin 
(from avena, the oat). Oatmeal, the ground and sifted flour of the 
grain, is not so white as wheaten fiour, and has a somewhat bitterish 
taste. Under the husk of the oat there is a thin cuticle or integu- 
ment, surrounding the central part, which is ground up with the meal, 
and not being sifted out, gives it a rough and harsh taste, and although 
the oatmeal gruel be strained, still a quantity of the sharp fragments 
of cuticle escape through the strainer. Grits, or groats, are oats in 
which the outer husk and cuticle are ground off and removed, so that 
grit gruel is 'smoother,' as it is termed. It is chiefly made into 
cakes, porridge, and gruel. 

450. Barley. — The composition of barley is represented as follows : 

Fine Barley Meal (Johnston). Barley (Poggailk), lator. 

Starch 68 Nitrogenous matters 10*655 

Fattymatter 2 Starch and dextrin 60-830 

Gluten, albumen, &c 14 Fatty matters 2*384 

"Water 14 Lignin 8779 

Ash 2 Mineral substances 2*623 



Water 15-229 



100 



EmnoF's analysis represents it as containing 4*62 of gum and 5*21 of 
sugar. Its husk or bran forms from 10 to 18 per cent, of its weight. 



GRAINS LEGUMINOUS SEEDS. 241 

The composition of barley has not been very carefully examined. It 
is reported to contain a good share of nitrogenous matter, but of what 
nature is not known. It is deficient in true gluten and behaves like 
oatmeal when washed with water. "When stripped of its husk or 
outer skin by a mill, it is called hulled or pot-ljcirley, and is used for 
making broth. After a considerable portion more of the kernel has been 
ground off, the rounded and polished grains are known as pearl-iarlcy. 

451. Rice is remarkable for being richest in starch and most de- 
ficient in oil of all the cultivated grains. Its flesh -producing elements 
are low, much lower than wheat or Indian corn, and less than half 
that of oats. Analysis gives the following results: 

Rice (Paykn). Rice (Pogoaile), 

Starch 86*7 Starcli, dextrin, sugar 74-470 

Gluten, &c 7'5 Nitrogenous matters 7'SOO 

Fatty matter 0-S Fatty matters 2-235 

Sugar and gum 0-5 Mineral -326 

Epidermis (skin) 8-4 Lignin 8-345 

Salinematter (ash) 0-9 Water 17-730 

Prof. JoKN'STOiT found five varieties to contain an average of 13"4 per 
cent, of water and but "41, that is less than half of one per cent, of 
ash. Mr. Horsfoed separated from some rice 15"14 per cent, of water, 
and 6'27 per cent, of nitrogenous matter in its ordinary state, and 7.4 
per cent, in its dry state. It is usually presented to us in market 
hulled, or freed from its husk, and is used whole, being but rarely 
ground into flour. 

452. Backwheat. — The composition of this grain has not been satis- 
factorily elucidated; there remains considerable discrepancy in the 
results of its analysis, Zenneok found that in the dry state it con- 
sisted of — 

Husk 26-9 

Gluten, &c 10-7 

Starch 52-3 

Sugar and gum S-3 

Fatty matter 0*4 

Tlie gluten is here supposed to bo estimated too high. Uoesford ob- 
tained from buckwheat flour in the natural state (that is, not dried) : 

Water 1512 

Starch 6505 

Protein 5-84 

B.— L.eguiniuous Seeds. 

453. Conipositiou of Peas.— Seeds obtained from pods are called 
leguminous. Of this class we are only concerned with peas and 

11 



242 GENERAL PKOrERTIES OF ALIMENTARY SUBSTANCES. 

Leans. They resemble mucli in composition the cereal grains, bn' are 
more highly nntritivo ; indeed, they afford the most concentrated form 
of vegetable nourishment. The roasted cMch-pea of the East is con- 
sidered to be more capable of sustaining life, weight for -weight, than 
any other kind of food ; hence, it is preferred by travellers about to 
cross the deserts, as the least bulky and heavy form of diet. Accp^'tl- 
ing to HoESFOED and Keockeb : 

A Tatle Pea yielded : A Field Pea gave : 

Albumen and casein 2S-02 Albumen and casein 29'18 

Starch SS-81 Starch 66-23 

Gum 28-50 Gum 60-23 

Skin T-65 Skin 6-11 

Ash 3-18 Ash ' 2-79 

According to Poggaile, field peas that had been deprived of 9*5(? i 
envelope, contained : 

Nitrogenous matters 21"670 

Starch, dextrin, and sugar 57-650 

Fatty matters 1-920 

Lignin 3218 

Mineral 2-802 

Water 12-740 

He found also in very soft green peas : 

Nitrogenous matters 38-85 

Older than the above 34-17 

PJpened 27-72 

Prof. JouNSTON states that the proportion of nitrogenous, or flesh- 
forming matter, in both peas and beans, is on an average about 24 per 
cent., and of oil about two per cent. The nitrogenous element of 
peas and beans is not glutinous, and consists chiefly of vegetable 
casein. They are hence incapable of making bread. From their 
high proportion of nitrogenous constituents, peas and beans are ex- 
tremely nutritious, ranking first among concentrated strength-impart- 
ing foods. Tiiey are considered difficult of digestion, and of a con- 
stipating quality, which requires to be corrected by admixture with 
other kinds of food. The varieties are numerous, with wide differen- 
ences of fiavor and softness when cooked, and they probably differ 
equally in composition. We have before stated, that in consequence 
of its abundance of casein, the Chinese make it up into a kind of 
vegetable cheese (424). 

454. Composition of Beans. — The composition of beans varies but 
little from that of peas. The authorities above cited (HoESFORn and 
Ejjooker) give tlie following results: 



LEGUMINOUS SEEDS — FKUITS. 243 

Beans (Hoesfoed and Keockee). Table Bean. Large White Bean. 

Vegetable casein and albumen 28-54 29'31 

Stareb 37-50 66-lT 

Gum 29-20 66-lT 

Skin 4-11 4-41 

Asb 4-33 4-01 

The peas and beans in this analysis were dried at 212°, and lost an 
average of 15.53 per cent, of moisture. 

455. Bone-producing material in Peas and Beans. — By reference to the 
preceding analytical results, it will be seen that the ash, or mineral 
constituents of peas and beans, from which the earthy part of bones 
is derived, is considerable, but larger in beans than in peas. 

Will and Feksiniub' analyses of the ash of Three analyses of the ash of beans gave the 
peas gave : following average result : 

Potasb 39-51 Potash 29-62 

Soda 3-93 Soda 13-31 

Lime 5-91 Lime 6-11 

Magnesia 6-48 Magnesia 8-95 

Oxide of iron 1-05 Oxide of iron 0-93 

Pbospboric acid 84-50 Phospboric acid 4-84 

Common salt 3-71 Cblorine 1'18 

Sulpburic acid 4-91 Sulpburic acid 1-4.3 

SUica 5-34 

C— Fruits. 

456. Tlieir General Composition. — Although fruits are extensively 
used as articles of diet, yet as staple sources of nutrition they bear no 
comparison to the grains. They consist of pulpy masses, which are 
nearly all water, and are prized far more for those properties which 
relate them to the taste than for nourishing or strengthening power. 
They generally consist of from 75 to 95 per cent, water, from 1 to 15 
or 20 per cent, fruit sugar, organic acids in variable proportions (414) • 
in combination chiefly with lime and potash, pectine, or the jelly- 
producing principle, ligneous skins and cores, with peculiar aromatic 
and coloring principles of infinite shades of diversity. The unripe 
fruits contain a larger proportion of water and acid, and a less amount 
of sugar than the natural fruits. As they contain so great a proportion 
of watery juices, they are very prone to change, and thus exhibit little 
constancy of composition. From this circumstance, and the number- 
less varieties of fruits that are catalogued, and also from the fiict tliat 
comparatively little attention has been given to this branch of organic 
chemistry, our knowledge of the exact composition of fruits is very 
imperfect. 

457. Composition of Apples. — Every one will understand that the 



244 GENERAL PROPERTIES OF ALIMENTARY SUBSTANCES. 

various sorts of ajiples difter mucli in composition, j'et in an average 
condition 100 lbs. of fresh apples contain abont 3 "2 lbs. of fibre, 0*2 
lbs. of gluten, fat, and wax, 0*16 of casein, 1-4 of albumen, 3"1 of 
dextrine, 8 3 of sugar, 0'3 of malic acid, 82'6G of water. Besides the 
above mentioned bodies, the apple contains a small quantity of tannic 
and gallic acid — most in the russets. To these acids apples owe their 
astringency of taste, and the blackening iron or steel instruments used 
to cut them. The following is the proportion of water and dry matter 
in several varieties of apples, according to Sallsbuet's examination. 



Talman Sweeting. 


Greening. 


Swarr Apple. 


Roxbury Russet. 


Englist Russet, 


"Water 81-52 


82-85 


84-75 


81-35 


79-21 


Dry Matter. . 18.43 


17-15 


15-25 


18-65 


20-79 



Muskmelon. 


Cucumber. 


90-98 


96-36 


901 


3-63 



The percentage of ash in the apple is small, yet it is rich in phosphoric 
and sulphuric acids, potash, and soda. The proportions of water and 
dry matter have also been determined in the following substances : 

Watermelon. 

"Water 9489 

Dry Matter 510 

The dry matter of melons contains quite a large percentage of albumen, 
casein, sugar, and dextrin, with a small quantity of acid. 

D.— licaves, L.eaf-Stalks, &c. 

458. Many kinds of leaves abound in principles adapted for animai 
nutrition, as is shown by the extent to which cattle are grown, sus- 
tained and fattened upon the grasses. Man makes use of leaves in hia 
diet to but a limited extent. Professor Johnston remarks, "leaves 
are generally rich in gluten; many of them, however, contain other 
substances in smaller quantity associated with the gluten, which are 
unpleasant to the taste, or act injuriously upon the general health, and 
therefore render them unfit for human food. Dried tea-leaves, for 
example, contain about 25 per cent, of gluten ; and therefore if tliey 
could be eaten with relish and digested readily, they would prove as 
strengthening as beans or peas." 

459. The Cabbage. — The same authority says of this vegetable : " It 
is especially nutritious. The dried leaf contains, according to my 
analysis, from thirty to thirty-five per cent, of gluten ; and is in this 
respect, therefore, more nutritious than any other vegetable food 
•which is consumed to a large extent by men and animals. I know, 
indeed, of only two exceptions, — the mushroom, winch in its dry mat- 
ter contains sometimes as much as 56 per cent, of gluten, and the 
di'ied cauhflower in which the gluten rises, as high as 64 per cent." 



LEAVES, LEAF-STALKS, BOOTS, ETC. 246 

The cabbage and cauliflower lose in drying more than 90 per cent, of 
water ; and the dried residue, according to Pebeiba, is remarkably 
rich in sulphur as weU as nitrogen. The plant decays quickly, and 
gives out a strong odor of putrefaction, owing to its nitrogenous and 
sulphurous compounds. Decayed, cabbage leaves should therefore 
not be allowed, to remain in cellars, or lie about in the vicinity of 
dwellings. 

460. Lettnce Leaves are much used at table as a salad. The young 
leaves contain a bland, cooling juice ; but as the plant advances, its 
milky juice becomes bitter, and is foimd to contain opium. In this 
stage it has a slight tendency to promote sleep. The water-cress, leaves 
of white mustard and of common cress, probably owe their pungency 
to a minute portion of sulphurized volatile oil, analogous to that found 
in horseradish. The stalks of many kinds of leaves, as spinach, 
turnip-to2)s, potato-tops, cowslips, &g., are used as greens, but their 
peculiar characters have not been ascertained. The stalks of rhuharJ), 
used for pies, puddings, &c., like apples and gooseberries, contain 
much malic and oxalic acid in combination with lime and potash. 
The proportion of water, dry matter, and ash, in the rhubarb stalk, 
celery, and vegetable oyster, is as follows : 

Rhubarb Stalks. Celery. Vegetable Oyster. 

Water 89-50 88-22 84-40 

DryMatter 10-50 11-77 15-54 

Ash 1-13 

Half the dry matter consists of malic, tartaric, and oxalic acids, with 
fibre, sugar, albumen, and casein. 

JE«— RootS) Tubers^ Bulbs and Shoots. 

461. Compositiou of Potatoes — Water. — This is the most widely culti- 
vated and important for dietetical purposes of aU the root tribe, and 
has been more carefully examined than any other. Like fruits and 
leaves its leading constituent is water, which composes about three- 
quarters of its weight. Young, unripe potatoes contain more water 
than those fuUy grown, and it has been found that the ' rose ' end of 
the potato, or that part from Avhich the young shoots spring, contains 
more water than the ' heel ' or part by which it is attached to the 
rootlet. KoETE examined 55 varieties of potato and found them to 
contain 75 per cent, of water and 25 of solid matter. Professor 
JoHNSTOK gathered from 27 analyses made in his laboratory tlie fol- 
lowing results. Greatest proportion of water in young potatoes, 82 
per cent. ; largest proportion in fuU grown potatoes, 68"6 per cent. 



24 G GKNEKAL PROPERTIES OF ALIMENTARY SUBSTANCES. 

He gives the mean of 51 determinations upon potatoes of all ages— as 
water 76 per cent., dry matter 24. 

4C2. St.nrch in Potatoes. — A large part of the solid matter in potatoes 
consists of starch. JonxsTOX states as tlie results of numerous expe- 
riments, that the proportion is in the natural state 64"20 per cent. 
SiEMEXs ascertained the proportion of starch in 66 varieties to range 
between 19"25 and 11-16 per cent. ; the average being 15*98. These 
proportions, however, vary with the kind of potato, soil, season, 
and other circumstances. The heel end usually contains more starch 
than the rose end. The weight of potatoes and their proportion of 
starch diminishes by keeping. Patkn found the same variety to yield 
of starch in 

October 17'2 per cent. February 15"2 per cent. 

November 16-8 " March 15 " 

December 15-6 " April 14*5 " 

January 15"5 

Other experiments would seem to show that there is rather an increase 
after digging ; but all examinations agree, that as vegetation becomes 
active in the spring, the buds begin to grow at tlie expense of the 
starch contained in the tuber, and hence at this season potatoes are 
less mealy, and not so much esteemed for table use. 

463. Flesli-prodncing constituents of Potatoes. — The potato contains a 
considerable proportion of nitrogenous matter in the threefold form 
of albumen, casein, and gluten, as it exists in the grains. They exist 
dissolved in its juices. There is more of the casein than of the otlier 
elements. Johnstok gives the average of these constituents at l-4th 
per cent, in the natural state, and 5-8th per cent, when freed from 
water. But he acknowledges his mode of separating them to be Hable 
to error, so that the figures are probably too low. Hoesfoed, by a 
more accurate method, found the percentage of these compounds 
in the dry matter of potatoes to be — in white potatoes 9'96 per 
cent., in blue 7'66 per cent. He found also that not only is the pro- 
portion different in diifereut varieties, but that it is greater in young 
potatoes than in old ; and Boussixgault also found the proportion of 
the protein compounds to diminish the longer the potato is kept. 

464. Woody Fibre, Sugar, Gnui. — The proportion of fibre in the 
potato varies from 1\ to 10 per cent., and may be said to average 
about 3. Tlie fatty matter is also variable, but may be stated at about 
1 per cent. Sugar in the natural state about 3 '3, gum 0'55, or in the 
dry condition, sugar 13'47, guin 2-25. 

465. Average Composition of Solid or Dry Matt«r of Potato. — This is 
summed up by Professor Johnston in round numbers as follows : . 



THE POTATO AND ONION. 247 

Starch 64 

Sugar and gum 15 

Protein compounds k 9 

Fat 1 

Fibre 11 

Total 100 

The dry potato, therefore, is about equal ia nutritive value to rice, and 
is not far behind the average of our finer varieties of wlieaten flour. 
The juice of potatoes is acid ; it was formerly supposed to contain 
citric acid, but it is now ascertained to be due to malic acid, and per- 
haps the sulphuric and phosphoric found in the ash. Potatoes also 
contain a small portion of asparagin, the peculiar principle of asparagus. 
When potatoes are freed from their large excess of water, so as to 
bring them into just comparison with the grains in composition, they 
are found to contain quite a large percentage of mineral matter left as 
ash — the average of six determinations giving 3'92 per cent. The 
constituents of these six samples give an average as follows : 

Potash 55-75 

Soda 1-86 

Magnesia 5'28 

Lime 207 

Phosphoric acid 1257 

Sulphuric acid 13'64 

Silica 4-23 

Peroxide of iron 0-52 

Common salt 7'01 

The carbonic acid, which was from 6 to 12 per cent., was deducted. 
The mineral matter of the potato seems to be thus distinguished from 
that of the grains by its large proportion of potash, sulphuric acid, 
and common salt, and its lesser quantity of phosphoric acid and mag- 
nesia. 

466. The Onion. — This bulbous root abounds in nitrogenous matter; 
when dried, it has been found to yield from 25 to 30 per cent. It 
is therefore highly nutritive. It contains a strong-smelling sulphur- 
ized oil, the same that gives its powerful odor to the garlic. The con- 
stituents of the onion are thus stated by Peeeiea : 

Volatile oil. Woody fibre, 

Uncrystallizable sugar, Poetic and i)hosiihciric acid, 

Gum, Phosphate and carbonate of limo, 

Vegetable albumen. Iron. 

467. Beets. — The varieties of beets of course differ in composition, 
but they all contain much sugar. Their nutritive qualities are not 
well determined. Beetroot is represented as containing 81 per cent 



248 GENERAL PEOPEETIES OF ALIMENTARY SUBSrANCES. 

of water, 10"20 of sugar, aud 2"03 of nitrogenous matter. In the long 
blood-beet there is 89'09 per cent, of Avater, and 10-90 of dry matter. 
4G8. Tnrnips, Carrots, Parsnips. — Chemistry has hitherto cast but 
an uncertain light upon the composition of this class of substances. It 
appears from the best determinations, that the pro2)ortion of solid mat- 
ter in several roots is as follows: 

White Turnips lOi 

Tellow do 13i 

Mangel-wurzel 15 

Carrot 14 

The dry substance of these roots is much !'ower than that of the pota- 
to, which ranges at 25 per cent. Yet the flesh-forming constituent? 
of dried turnips much exceed those of Ihe potato, as the following com- 
parison shows. 

Protein Compounds. 

The dried potato 8 per cent. 

Tellow turnip 9} do. 

Mangel-wurzel 15J do. 

The nitrogenous matter of dried mangel-wurzel being nearly twice 
as great as in the dried jjotato. In the carrot the proportion of water 
is 85'78, and dry matter 14-22. According to Ceome, the parsnip 
contains — 

starch 1-8 

Albumen 2-1 

Gum 61 

Sugar 5-5 

Fibre 51 

Water 79-4 

Total 10000 



4. CoMPoiTND Aliments — Animal Food. 
A. — Constituents of Meat. 

469. — Various parts of animal bodies contribute materials for diet; 
the flesh and fat chiefly, but nearly ?J1 other portions, blood, intestines, 
membranes, bones, and skin, more or less. The staple constituents 
of animal food are fibrin, albumen, gelatin, fat, salts, and water, and 
in the case of milk, casein and sugar. 

470. Composition of Flesh-meat. — This is generally understood to sig- 
nify the muscular or lean parts of cattle, surrounded by fat, and con- 
taining more or less bone. The muscles consist of fibrin ; they are 
separated into bundles by membranes, and into larger separate masses 
by cellular tissues, in which fat is deposited. The fleshy mass is pene- 



CONSTITUENTS OF MEAT. 249 

trated by a network of blood-vessels and nerves, and the whole is dis- 
tended by water, which composes about three-fourths of the weight 
of the meat. The coraj^osition of the muscular flesh of different ani- 
mals, according to Mi-. Brande, is as follows: 

Water. Albumen and Fibrin. Gelatin. Total solid matter. 

Beef T4 20 6 26 

Veal 75 19 6 25 

Mutton Tl 22 7 29 

Pork 76 19 5 M 

Chicken 73 20 7 27 

Cod 79 14 7 21 

These results give an average of very neurly 75 per cent, water. 
LiEBiG assumes it at 74, with 26 per cent, of dry matter. The ratio of 
water in meat, fowl, and fish, is quite uniform, ranging from 70 to 80 
per cent., but the proportion of the other constituents, muscular fibre, 
fat, and bone, exhibits the widest possible diversity. In some animals, 
more especially wild ones, as deer, &c., there may be hardly a trace 
of oily matter, while swine are often fed until the animal becomes one 
morbid and unwieldy mass of fat. The pure muscular flesh of ordi- 
nary meat, with all its visible fat separated, is assumed by Knapp and 
LiEBiG to contain still about 8 per cent, of fat. In beef and mutton, 
such as is met with in our markets, from a third to a fourth of tho 
whole dead weight generally consists of fat. — (Johnston.) 

471. Jnice of Flesh. — The true color of the fibrin of meat is white, 
yet flesh is most commonly of a reddish color (flesh-color). This is duo 
to a certain portion of the coloring matter of the blood, by which it is 
stained. Yet the liquid of meat is not blood ; when that has been 
withdrawn from the animal, and the blood-vessels are empty, there 
remains diffused through the muscular mass a peculiar liquid, known 
as the juice of flesh. It consists of the water of flesh, containing about 
5 per cent, of dissolved substances, one-half of which is albumen, and 
the other half is composed of several compounds, not yet examined. 
The juice of flesh may be separated by finely mincing the meat, soak- 
ing it in water, and pressing it. The solid residue which remains after 
all the soluble matter has been thus removed, is tasteless, inodorous, 
and white like fish. The separated juice is uniformly and strongly 
£x;id, from the presence of lactic and phoshporic acids, hence it is in 
the opposite state to tliat of the blood, which is invariably alkaline. 
The juice of flesh contains the savory principles which give taste to 
meat, and which cause it to differ in different animals. It also con- 
tains two remai'kablo substances, called hreatitie and Creatinine, nitro- 
genous compounds, which may be crystallized. The quantity yielded 

II* 



250 GENERAL PROPERTIES OF ALIMENTARY SUBSTANCES. 

is variable in different kinds of flesh, but in all is extremely small. 
Kreatine is a neutral or indifferent substance, -while kreatinine is a 
powerful organic base, of a similar nature with theine and cafeine of tea 
and coffee. 

472. Blood, Bones, and Internal Organs. — The leading constituents of 
blood are the same as flesh ; it contains only some three per cent, more 
of water. Its nitrogenous matter, however, is chiefly liquid albu- 
men. Blood has been called liquid flesh, and flesh solidified blood. 
About half the weight of bones is mineral matter, lime combined 
with phosphoric acid, forming phosphate of lime — the substance that 
we have seen to abound so greatly in the ash of grains. The other 
half of bones is gelatin, the thickening principle of soups (glue). It 
is sometimes partially extracted for this purpose by boiling. Marrow 
is a fatty substance, enclosed in very fine cellular tissue within the 
bone. Skin, cartilage, and membrane, yield much gelatin. The 
tongue and Tieart are muscular organs, agreeing in dietetical proper- 
ties with lean flesh. Bracoonnot's analysis of the liver gives 68 per 
cent, of water, and 26 of nitrogenous matter; it also contains oil. 
The Irain is a nervous mass, containing 80 per cent, water, some al- 
bumen, and much of a peculiar phosphoric oily acid. The stomacJia 
of ruminating animals which yield tripe, are principally composed of 
fibrin, albumen, and water. 

473. Composition of Eggs. — The eggshell is a compound of lime, not 
the phosphate as exists in bones, but chiefly carbonate of lime. It is 
porous, so as to admit of air for the wants of the young animal in 
hatching, and usually weighs about one-tenth of the entire egg. The 
white of egg consists of water containing 15 or 20 per cent, of albumen. 
The yolk is water and albumen, but contains, also, a large proportion 
(two-thirds of the dried yolk) of a bright yellow oil, containing sulphur 
and phosphoric compounds. A common-sized hen's-egg Aveighs about 
a thousand grains, of which the shell weighs 100, the wliite 600, and 
the yolk 300. The composition of its contents is : 

Water 74 

Albamen 14 

Fat 10-5 

Ash (salts) 1-5 

Total 100 

B.— Production and Composition of Milk. 

474. What it Contains. — This familiar liquid consists of oil or butter, 
BUgar, casein or the cheesy principle, and salts, with a large proportion 
of water. The sugar, casein, and salts are dissolved in the watei*, 



PKODTJCTION AND COMPOSITION OF MILK. 251 

wTiile the butter is not, but exists diflused through the liquid iii the 
form of numberless extremely minute globules. They cannot be seen 
by tlie naked eye. "When the light falls upon them they diffuse it in 
all directions, so that the mass appear opaque and white. Yiewcd 
by a microscope, the globules appear floating in a transparent hquid. 
In respect of its sugar, casein, and salts, milk is a solution ; but with 
reference to its oily part, it is an emulsion. It is heavier than water 
in the proportion of about 103 to 100, although it differs considerably 
in specific gravity. Wlien first drawn it is slightly alkaline and has a 
sweetish taste, which is due to the sugar of milk. 

475. Proportion of its Elements. — This is variable. It generally con- 
tains about 86 per cent, water, 4 to 7 of casein, 3-5 to 5-5 of butter, 
and 3 to 5-5 of sugar of milk and salts. The following are analyses 
by Henuy and Chevaliek: 

Cow. Womnn. 

Casein 4-48 1-52 

Butter 813 355 

Milksiigar 4-47 6-50 

Salts -CO 0-45 

Water 87-02 87-98 

The following are Hadlein's results : — The second column is thoi 
average of two analyses. 

Cow's Milk. Woman's Milk.* 

Butter 3 2-353 

Sugar of milk and salts soluble in alcohol 4-6 S.75 . 

Casein and insoluble salts 5-1 2-90 

Water 873 90-50 

476. Circumstances Inflneneing tlie Quality of Milk. — Both the quantity 
and quality of milk are influenced by various conditions apper- 
taining to the animal. Its food exerts a powerful control in this 
respect. Green succulent food is more favorable to the production of 
milk than dry, and R. D. Thomson's experiments go to show that of 
dry food, the richest in nitrogenous matter best promotes the milk 
secretion. Platfaib was led, by his brief experiments, to conclude 
that food low in nitrogenous matters (as potatoes) yielded a largo 
quantity of milk which was rich in butter, and that quiet (stall feed- 
ing) had the same effect, whilst cows grazing in the open air upon 
poor pasture, and consequently obliged to take much exercise, yielded 

* The milk of women from 15 to 20 years of age, contains more solid constituents 
than of women between 80 and 40. Women with dark hair also give a richer milk than 
women with light hair. In acute diseases the sugar decreases one-fourth, and the curd 
Increases one-fourth ; while iu chronic affections the butter increases one-fourth, and 
the casein slightly diminishes. In both classes of diseases the proportion of saline mattei 
diminishes. — (Johnston.) 



252 GENIERAL PROPERTIES OF ALIMENTAUT SUBSTANCES. 

milk ricli in casein. It appeared from Thomson's observations, tliat 
the produce of milk of a cow, with uniform diet, gradually diminished, 
and increased again by a change of diet. It is well known that a cow 
fed upon one pasture wUl yield more cheese, while upon another it 
will give more butter. Hence the practice in dairy districts of al- 
lowing the animal to roam over a wide extent of pasture to seek out 
for itself the kind of herbage necessary to the production of the richest 
milk ; hence, also, the propriety of adding artificial food to that de- 
rived from grazing. Plants and weeds found scattered in many 
pastures are apt to affect, injuriously, the quality and taste of the milk. 
Butter is especially liable to be deteriorated in this way. An observ- 
ing dairy -manager remarks as follows: "If a cow. be fed on ruta-baga, 
her butter and milk partake of that flavor. If she feeds on pastures 
where leeks, garlicks, and wUd onions grow, there will be a still more 
offensive flavor. If she feeds in pastures where she can get a bite of 
brier leaves, beech or apple-tree leaves, or any thing of the kind, it 
injuriously affects the flavor of the butter though not to the same 
extent, and would scarcely be perceptible for immediate use. So 
with red clover. Butter made from cows fed on red clover is good 
when first made, but when laid down in packages, six months or a 
year, it seems to have lost all its flavor, and generally becomes more 
or less rancid as the clover on which the cow fed was of rank and 
rapid growth." — (A. B. Dickinson.) 

477. Distance from the time of calving, — The colostrum, or fii-st milk 
which the cow gives for several days after the birth of her young, 
differs from normal milk. Geegoey states that it contains from 15 to 
25 per cent, of albumen, Avith less casein, butter, and sugar of milk 
A mucli larger quantity of milk is yielded m the first two month? 
after calving, than at the subsequent periods ; the decrease is stated 
as follows, according to Ayton : 

Qnni-ts per day. Quart*. 

First 50 days 24 or in all 1200 

.Second " .... 20 " " 1000 

Third " 14 " " 700 

Fourth " 8 " " 400 

Fifth " 8 " " 400 

Sixth " 6 " " 300 

and at the end of ten months, they become nearly or altogether dry. 

478. Time of year, age aud condition of the animal. — In spring, milk is 
finest and most abundant. Moist and temperate climates and seasons 
are favorable to its production. In dry seasons the quantity is less, 
but the quality is riclier. Speengel states that cool weather favors 
the production of cheese and sugar in the milk, while hot weathef 



PR^-DUCriON Am) COMPOSITION OF MILK. 253 

increases the product of butter. The poorer the apparent condi- 
tion of the cow, good food being given, the richer, in general, is the 
milk ; bnt it becomes sensibly poorer when she shows a tendency to 
fatten. A state of comparative repose is favorable to all the impoi'- 
tant functions of a healthy animal. Any thing which frets, disturbs, 
torments, or renders her uneasy, afltects these functions, and among 
other results, lessens the quantity, or changes the quality of the milk. 
Such is observed to be the case when the cow has been newly de- 
prived of her calf — when she is taken from her companions in the 
pasture-field — when her usual place in the cow^-house is changed — 
when she is kept long in the stall after spring has arrived — when she 
is hunted in the field, or tormented by insects, or when any other 
circumstance occurs by which irritation or restlessness is caused, 
either of a temporary or of a permanent character. — (Johnston.) 

479. Prodttction and Composition of Cream. — We have stated that 
butter exists in milk, as a fatty emulsion ; that is, not dissolved, but 
floating as exceedingly minute globules throughout the watery mass. 
These butter globules are lighter than Avater, and hence, when the 
milk is suflered to stand undisturbed, they slowly rise to the sur- 
face, forming cream. The oil-globules of cream do not coalesce or 
run together, they are always separated from each other, and sur- 
rounded by the soluble ingredients of milk; while at the same time, 
the body of the milk never beco^nes perfectly clear by the complete 
separation of these globules. Hence, cream may be viewed as milk 
rich in butter, and skimmed milk as containing little butter. It is 
sr.'^posed by some, that the butter particles are in some way invested 
or enclosed with casein ; at all events, a quantity of cheesy matter 
rises with the oil-globules. Its proportion in cream depends upon the 
richness of the milk, and upon the temperature at which it is kept 
during the rising of the cream. In cool weather, the fatty matter will 
bring up with it a larger quantity of the curd, and form a thicker cream. 

480. Conditions of the Formation of Cream. — The globules of butter 
being extremely minute, and but slightly lighter than the surround- 
ing liquid, which is at the same time somewhat viscid or thick, they 
of course ascend but slowly to the surface. The larger globules of 
butter, which rise with greater ease, mount first to the surface. If 
the first layer of cream, consisting of these largest particles, be taken 
off after 6 or 12 hours, it aftbrds a richer, fresher, and more palatable 
butter than if collected after 24 or 30 hours standing. Milk is, there- 
fore, sometimes skimmed twice, and made to yield two qualities of but- 
ter. Tlie deeper the milk, the greater the difficulty with which tho 



254 GENEEAL PROrERTIES OF ALIMENTARY SUBSTANCES. 

oily matter ascends through it ; hence, it is customary to set the milk 
aside in shallow pans, so that it may not be more than two or three 
inches in depth ; hence, if it is desired to prevent the formation of cream, 
the milk should he kept in deep vessels. Te?H^cra^«?T powerfully in- 
fluences the formation of cream, or the rapidity with which it rises. 
Ileat, by increasing the thinness and limpidity of the liquid, aud the 
lightness of the oil-globules, favors their ready ascent ; while cold, by 
thickening the liquid, and solidifying the oil, greatly retards their sepa- 
ration. Hence it is said, that fi-om the same milk an equal quantity of 
cream may be extracted, in a much shorter time during warm than dur- 
ing cold weather ; that, for example, milk may be perfectly creamed 

In 36 hours when the temperature of the air is 50° P. 

"24 " " " 55° 

" 18 to 20 " " " 63* 

" 10 to 12 " " " 11' 

while at a temperature of 34° to 37° (two to five degrees above freez- 
ing), milk may be kept for three weeks, without throwing up any 
notable quantity of cream. — (Speengel.) 

481. Milk Creams before it is taken from the Cow. — This spontaneous 
tendency of milk to separate itself mechanically into two sorts or 
qualities, explains the remai'kable difference in the richness of milk 
withdrawn at different stages of the milking process. The glands in 
the teats of the animals, which secrete the milk, are vessels interlaced 
Avith each other in such a way as to form hollow spaces or reservoirs 
which distend as the milk is secreted. In these reservoirs the same 
thing takes place as occurs in an open vessel, and Avith still more 
facility as the temperature is up to blood heat (98°) — the rich creamy 
portion rises above, while the poorer milk falls below. Ilence that 
which is first draw'n is of an inferior quality, while that which is last 
drawn, the strippings or afterings^ abounds in cream. Professor An- 
derson states, that compared with the first milk the same measure of 
the last will give a^^ least eight, and often sixteen times as much cream, 
Tiic later experiments of Eeiset show, that where the milkings are 11 
or 12 hours apart, the quantity of butter in the last drawn milk is 
from three to twelve times greater than that obtained from the first 
drawn milk. Where the milkings were more often, the difference 
became less. As milk before being taken from the cow is already 
partially separated — its richer from its poorer parts — the dairy man- 
ager should take advantage of this circumstance, and not commingle 
in the same vessel the already half-creamed milk, if the object is the 
separation of butter. It has been shown that more cream is obtained 



PRODUCTION AND COMPOSITION OF MILK. 



25£ 




by keeping the milk in separate portions as it is drawn, and setting 
these aside to throw up their cream in separate vessels, than when 
the whole milking is mixed together. Moreover, the intimate mixture 
of the richer and poorer portions not only reduces the fig. go. 
quantity of cream that may be separated, but much delays 
the operation which, in hot weather, when milk soon 
sours, is objectionable. 

482. Detcrmming the valne of Milk. — ^Its value is propor- 
tional to the amount of its solid alimentary constituents, 
and is liable to variation, according to circumstances. If 
butter is to be manufactured from it, that is most valuable 
which contains most oily matter ; if cheese is desired, 
then that which contains most casein. Milk is heavier 
than water, and the richer it is the heaver it is ; hence it 
has been attempted to make the latter quality a guide 
to the former. Its weight compared with water, or spe- 
cijic gravity^ is determined by the hydrometer (Fig. 96). A 
tin or gloss cylinder is filled with milk to be tested, and 
the hydrometer, a glass bulb with a stem above, is placed ^ '^°™® "" 
in it ; the lighter the milk, the deeper it sinks ; the heavier it is, the 
higher it floats. A scale is marked upon 
the stem, which indicates at once how 
far the weight of the milk rises above 
pm-e water. Yet the results of the instru- 
ment are to be received with caution. 
Milks, though pure, differ naturally in 
specific gravity ; while it is easy to add 
adulterating substances that shall in- 
crease their weight, thus causing the 
hydrometer to report them rich. Yet 
as giving an important indication it has 
value, and with experience and judgment, 
may be made useful.* An instrument 
called the lactometer (milk measurer) 
has been used to determine the propor- 
tion of cream. It consists of a glass 
tube ten or twelve inches long, marked 
off and numbered into a hundred spaces. 
The tube being filled with milk to the 
top space, is suflered to stand until the I*ctomet«r. 

♦ Made by Tagliabue, of New York. 



Fig. 97. 





256 CUUNAEY CHANGES OF ALIMENTARY SUBSTANCES. 

cream rises to the surface, when its per cent, proportion is at once 
seen. It will answer if only the upper portion of the tube be marked 
as shown in Fig. 97. The percentage of cream, that is, the thickness 
of its stratum at the top of the tube, varies considerably. We have 
found the average to be 8| per cent., although samples are liable to 
range much above and below this number.* If the milk has been 
mixed, say with one-third water, the cream will fall to 6, if with one- 
half, it may fall to 5 per cent. 

483. Blineral Matter in Blilk. — The proportion of salts in milk 
averages about half per cent. ; that is, 200 lbs. when dried and burned 
will yield 1 lb. of ash. The composition of this ash is shown by tbo 
analysis of Haidlein, who obtained from 1000 lbs. of milk 

1 8 

Phosphate of lime 2-31 lbs. 3-44 1 |s. 

Phosphate of magnesia 042 " 0'64 ''' 

Phosphate of peroxide of iron 0'07 " 0'07 " 

Chloride of potassium 1'44 " 1'83 " 

Chloride of sodium 0-24 " 0-34 " 

Free soda 0-42 " 0-45 " 

Total 4-90 6-77 

III.— CULINARr CHANGES OF ALIMENTARY SUBSTANCES. 

1. COMBINIXG THE ELEMENTS OF BeEAD. 

484. General Objects of Culinary Art. — "We have seen that the ma- 
terials employed as human food consist of various organized substances 
derived from the vegetable and animal kingdoms, grains, roots, stalks, 
leaves, flowers and fruit, with flesh, fat, milk, eggs, &c. &v\ But few of 
these substances are best adapted for food in the condition in which they 
occur naturally. They are either too hard, too tough, insipid or injuri 
ous, and require to undergo various changes before they can be properly 
digested. Most foods, therefore, must be subjected to processes of 
manufacture or cookery before being eaten. In their culinary prep- 
aration, numerous mechanical and chemical alterations are effect- 
ed, in various ways; but the changes are chiefly wrought by means of 
water and heat. Water softens some substances, dissolves others, some- 
times extracts injurious principles, and serves an important purpose 
in bringing materials into such a relation that they may act chemically 
upon each other. Heat, applied through the medium of water, or in va- 
rious ways and degrees, is the chief agent of culinary transformations. 
Another proper object of cooking is the preparation of palatable dishes, 

* The number given by tlie lactomotor will, from the nature of the case, be somewhat 
under the truth, as the butter globules do not all ascend through the long column of milli. 



COMBINING THE ELEMENTS OF ]!REAr>. 251! 

from the crude, tasteless, or even offensive substances furnished by 
nature. This involves, not only the alterations produced by water and 
heat, but the adniixtui-e of various sapid and flavoring ingredients, 
which increase the savory qualities of food. The cereal grains, con- 
verted into flour and meal, are to be prepared for mastication, mixture 
"with the saliva, and stomach digestion. This end is best accomplished 
by converting them into bread, while at the same time they assume a 
portable and convenient form, and are capable of being preserved for 
a considerable time. Bread is made, as is well known, by first incor- 
porating water with the flour, and making it into dough., and then by 
various means causing it to rise, that is, to expand into a light, spongy 
mass, when, after being moulded into loaves, it is finally submitted to 
the action of heat in an oven, or baked. "We shall consider the suc- 
cessive steps of this important process, in the order of their occuiTcnce ; 
and as the flour of wheat is the staple article in this country for the 
manufacture of bread, it will occupy our first and principal attention. 
485. Water absorbed in making Dongh. — The addition of much water 
to flour forms a thick liquid, called batter ; more flour admixed stiffens 
it to a sticky paste, and still more worked through it produces a firm 
dough. The water thus added to flour does not remain loosely associ- 
ated with it, but enters into intimate combination with its constitu- 
ents, forming a compound, and is not all evaporated or expelled by 
the subsequent high heat of baking. In the dough, the liquid performs 
its usual oflice of bringing the ingredients into that closer contact which 
is favorable to chemical activity. As water is thus made to become a 
permanent part of solid bread, it is important to understand in what 
proportion, and under what conditions, its absorption takes place. 
Baked bread that has been removed from the oven from 2 to 40 hours, 
loses, by thorough drying at 220,° from 43 to 45 per cent, of its 
weight, or an average of 44 per cent. If we assume the flour to con- 
tain naturally IG per cent, of water, 10| lbs. of the 44 that was lost 
belonged to the flour itself, Avhile 33^ lbs. were artificially added in 
making the dough. Thus — 

DTflo"' 56 I 

Water in flour naturally lOJ j * 

Water added in baking ZZ\ 

100 
Ten pounds of flour would thus absorb 5 lbs. of water, and yield 15 
lbs. of bread. Tlie best flours absorb more water than those of infe- 
rior quaUty. The amount with which they will combine is sup- 
posed to depend upon the proportion of gluten. In dry seasons flour 



258 CULINARY CHANGES OP ALIMENTARY SUBSTANCES. 

■Will bear more water tlian in Tret, and a thorough process of kneading 
will also cause the dough to absorb a larger quantity without becoming 
the less stiff on that account. Certain substances added to flour aug- 
ment its property of combining with water (521). 

486. Effects of the Kneading Process. — The purpose of water inter- 
mingled with rlour is to combine with and hydrate the starch, to dis- 
solve the sugar and albumen, and to moisten the minute par,ticles of 
dry gluten, so as to cause them to cement together, and thus bind the 
whole into a coherent mass. But, as only a certain limited quantity 
of water can be employed to produce these results, it is obvious that 
it must be carefully and thoroughly worked throughout the flour — this 
is called l-neadlng the dough, and is generally- performed with the 
hands. The process is laborious, and attempts have been often made 
to accomplish it by machinery, but hitherto without success. Flours 
differ so much in their dough-making properties, that judgment is re- 
quired in managing them. As the eye cannot penetrate into the inte- 
rior of tlie doughy mass to ascertain its condition, we have no guide 
equal to the sense of touch. Differences of consistence, foreign sub- 
stances, dry lumps of flour, are readily distinguished by the hand of 
the kneader, who is also by feeling able to control the gradual and 
perfect admixture of water, yeast, and flour, better than any machine 
yet devised. Much of the excellence of bread depends upon the 
thoroughness of the kneading, the reasons of which will soon be 
apparent. At first the dough is very adhesive, and clings to the fin- 
gers, but it becomes less so the longer the kneading is continued, and 
wlien the fist upon being withdrawn leaves its perfect impression in 
the dough, none of it adhering to the hand, the operation may be dis- 
continued. 

487. Bread from plain Flour and Water. — When dough, made by 
simply working up flour and water, is dried at common temperatures, 
a cake is produced, not very hard, but whicb is raw, insipid, and indi- 
gestible. If baked at 212° (ordinary steam heat), a portion of the 
starch becomes soluble, but the cake is dense, compact, and very difii- 
cult of digestion. If baked a^ a still higher heat, and afterward sub- 
jected to prolonged drying, we have the common sTiip-lrcad or sea- 
liscuit, which is made in thin cakes and never in large loaves, and 
which is very dry, hard, and difficult to masticate, although it has an 
agreeable taste, derived from the roasting of the surface of the dough. 
Bread prepared in this manner lacks two essential characters, — suflicient 
softness to be readily crushed in the mouth or chewed, and a looseness 
of texture or spouginess by which a largo surface is exposed to the 



BREAD RAISED BY FERMENTATION. 259 

action of the digestive juices in the stomach. To impart these quali- 
ties to bread, the dough is subjected to certain operations before bak- 
ing, Avhicli are technically called raising. The capability of being 
raised is due to the gluten. By the mechanical operation of kneading, 
the glutinous parts of the flour are rendered so elastic that the mass 
of dough is capable of expanding to twice or thrice its bulk without 
cracking or breaking. Various methods are employed for this nur- 
pose, which will now be noticed ; and first of fermentation : 

2. — Bread Raised by Feementatioit. 

488. Substances capable of Putrescence. — It is a remarkable property 
of the nitrogenous alimentary principles, that when in a moist state, 
and exposed to atmospheric oxygen, they speedily enter upon a state of 
change or rapid decay. They are of very complex composition (422), 
the attractions of their atoms being so delicately adjusted that 
slight disturbing forces easily overturn them. Oxygen of the air 
seizes upon the loosely held atoms, breaks up the chemical fabric, and 
produces from its ruins a new class of substances — the gaseovis pro- 
ducts of putrefaction. Thus, it is well known that flesh, blood, milk, 
cheese, dough, bread, all of which are rich in nitrogenous substances, 
will preserve their properties in the air only a short time, but pass 
into a state of putrescence, becoming sour and nauseous, and sending 
forth offensive exhalations. This change is called putrefaction, and 
the compounds which are liable to it, putrefialle substances. 

489. The Putrefactive change Contagions. — The other class of aliments, 
the non-nitrogenous, are in this respect of a very diflerent natui-e. 
They contain fewer atoms, lack the fickle element nitrogen, and have 
a simpler and firmer composition. "When pure starch, gum, sugar, oi 
oil, are exposed to the air in a moistened state, they exhibit little ten- 
dency to change, and give rise to none of the effects of putrefaction. 
Yet if placed in contact with putrefying substances, the change jjroves 
contagious; they catch it, and are themselves decomposed and de- 
stroyed. Hence, when the putrefiable substances are considered, luitJi 
reference to the effects tTicy produce upon the other class, they take a 
new name, and are caWad ferments. The communication of that con- 
dition of change from one class to , the other, is called fermentation, 
and the substances acted upon are named fermentable compounds. 
Thus, if some sugar bo dissolved in water, and a portion of putrefying 
dough, meat, or white of egg be added to \t, fermentation aais in; that 
is, the change is conmumicated to the sugar, the balance of its affini- 
ties is destroyed, and two new substances — one alcohol, containing all 



2G0 CULINARY CHANGES OF ALIMENTARY SUBSTANCES. 

tlie liydrogen of tlio sugar, and tlie other carbonic acid, containing 
two-thirds of its oxygen — are produced. 

490. Conditions of Fermentation. — When matter capable of putre- 
faction begins to change, decomposition rapidly spreads throughout 
the mass. If a small portion of putrefying substance be added to a 
large quantity, in which it has not commenced, the change extends 
until the whole becomes alike affected. But it is not so in fermenta- 
tion. The sugar cannot catch the infection and then go on decompos- 
ing itself. It can only break up into new compounds as it is acted 
upon, and when the limited quantity of ferment made use of is ex- 
hausted, or spent, the effect ceases, no matter what the amount of 
fermentable matter present. Two parts by weight of ferment decom- 
pose no more than one hundred of sugar. Temperature controls the 
rate or activity of fermentation. At 32° no action takes place ; at 45° 
it proceeds slowly ; at 70° to 86°, which is the proper range of warmth, 
it goes on rapidly. The operation may be stopped by the exhaustion 
of either the ferment or the sugar, by drying, by exposure of it to a 
boiling heat, and by various chemical substances, as volatile oils, sul- 
phurous acid, &c. 

491. Different kinds of Fermentation. — When nitrogenous matters 
are just beginning to decompose, the action is too feeble to establish 
the true alcoholic fermentation in solutions of sugar. Yet even in this 
early stage they can change the sugar, not breaking it to pieces so com- 
pletely, but splitting each of its atoms into two equal atoms of lactio 
acid, the sour principle of milk. This process is called the lactic acia 
fermentation, while that in which alcohol is produced is the xinous or 
alcoholic fermentation. If this be not checked, the process is liable to 
run on to another stage ; the ferment is capable of attacking the alco- 
hol itself, and converting it to acetic acid, the active principle of vine- 
gar. This is the acetous fermentation. There are several conditions 
of this acetous change. First, a spirituous or alcoholic solution ; second, 
a temperature from 80° to 90° ; third, a ferment to give impulse to 
the change ; and, fourth, access of air, as oxygen is rapidly absorbed 
in the process, combining with and oxidizing the alcohol. 

492. Dougli raised by Spontaneous Fermentation. — Now dough, as it con- 
tains both gluten and sugar, when moistened is capable of fermentation 
without adding any other substance. If simple flour and water be 
mixed and set aside in a warm place, after the lapse of several hours it 
will exhibit symptoms of internal chemical action, becoming sour from 
the formation of lactic acid, while minute bubbles appear, which are ow- 
ing to a gas set free within the dough. The changes are irregidar and un* 



BREAD RAISED BY FERMENTATION. 261 

certain, according to the proportion and condition of the constituents 
of the flour. They also proceed with greater or less rapidity at the 
surface or in the interior, accordingly as the parts are exposed to the 
cooling and oxidating influence of the air. Bread baked from such 
dough, is sour, heavy, and altogether bad. Yet the true vinous fer- 
mentation may be spontaneously established in the dough, by taking 
measures to quicken the action. If a small portion of flour and water 
be mixed to the consistency of batter (its half-fluid state being favor- 
able to rapid chemical change), and the mixture be placed in a jar or 
pitcher and set in a vessel of water, kept at a temperature from 100° 
to 110°, in the course of five or six hours decomposition will have set 
in, with a copious production of gas bubbles, which may be seen by 
the appearance of the batter when stirred. If this be now mixed and 
kneaded with a large mass of dough, moulded into loaves and set 
aside for an hour or two in a warm place, the dough will swell, or ' rise ' 
to a much larger bulk ; and when baked, will yield alight spongy bread. 
A little salt is usually added at first, which promotes the fermenta- 
tion, and hence, bread raised in this manner is called 'salt raised 
bread.' Milk is often used for mixing the flour, instead of water ; 
the product is then called ' milk-emptyings bread.' 

493. What makes the Dough rise ? — The cause of the rising is the 
vinous fermentation produced by the spontaneous change of the gluten 
or albumen which acts upon the sugar, breaking it up into alcohol and 
carbonic acid gas. If the fermentation is regular and equal, the knead- 
ing and intermixture thorough, and the dough kept suflSciently and 
uniformly warm, the production of gas will take place evenly through- 
out the dough, so that the bread when cut will exhibit numberless 
minute cavities or pores, equally distributed throughout. For its capa- 
bility of being raised, dough depends upon the elastic and extensible 
properties of its gluten, which is developed by the admixture of water 
with flour. Hence the proper quantity of water is that which im- 
parts to the gluten the greatest tenacity ; an excess of it lowering 
the adhesiveness of the glutinous particles. The toughness of the 
gluten prevents the small bubbles of gas from uniting into larger ones, 
or from rising to the surface. Being caught the instant they are pro- 
duced, and expanding in the exact spot where they are generated, tliey 
swell or raise the dough. All rising of bread depends upon this prin- 
ciple — the liberation of a gas evenly throughout the glutinous dougli. 
No matter what the mode of fermentation, or what the substances or 
agents employed instead of it, they all bring about the result in the 
same way. 



262 CULINAEY CHANGES OF ALIilENTAEY SUBSTANCES. 

494. Raising Dongh by Leaven. — But the mode of raising dougli bj 
spontaneous fermentation (492) is not sufficiently prompt and conve- 
nient ; we require some readier means of establishing immediate de- 
composition. If we take a piece of dough which has been kept suffi- 
ciently long to ferment and turn sour, and then knead it up thoroughly 
with a large lump of fresh dough, the whole of the latter will shortly 
enter into a uniform state of fermentation ; and if a little of this be re- 
served for tlie next baking, it may be worked into a fresh mass of dough, 
and in this way, active fermentation may be induced at any time. 
Fermenting dough thus used is called leaven. It may be made from 
any sort of flour, and is improved by the addition of pea and bean 
meal, which ferment easily. When properly, made, leaven may bo 
kept weeks or mouths fit for use, and by adding a portion of dough 
to the leaven, as large as that reserved for the bread-maker, the 
stock of leaven is always kept up. Although leaven when added 
to dough, awakens the true alcoholic fermentation, yet being in a sour 
state, it produces a portion of lactic acid, and often acetic acid ; the 
latter being mostly driven ofl? in the process of baking, while the 
former remains in the bread. Hence, bread made with leaven always 
has a distinctly sour taste, partly caused by the acid of the leaven it- 
self, and partly by the sour fermentation which it induces in the 
dough. It is difiicult to manage, and requires much skill to produce 
a good result. Leaven is but little used in this country, bread be- 
ing almost imiversaUy raised by means of yeast. 

3. Propeeties AifD Action of Yeast. 

495. Prodnction of Brewer's Yeast. — When grains are placed in the 
proper conditions of germination, that is, moistened and exposed to 
atmospheric oxygen at the proper temperature, a portion of their glu- 
ten is changed to the state of ferment, and acquires the property of 
transforming starch into sugar. Hence, seeds in germinating become 
sweet. Barley placed in these conditions, begins to germinate, swells, 
softens, and turns sweet ; it is then heated and dried, by which the 
process is stopped. Tlie barley is then called malt. It is next crushed 
or groimd and infused {masTied) in water at 1G0° so as to extract all 
the soluble matter it contains. The liquid (sicect-wort) is then boiled 
to coagulate the excess of vegetable albumen. Hops are added, to 
impart a bitter taste to the product (beer), and also to regulate the 
subsequent fermentation. The cooled wort is then run into the fer- 
menting vat, and yeast is added. "In three or four hours, bubbles of 
gas will be seen to rise from aU parts of the liquid ; a ring of froth, 



PKOPERTIES AND ACTION OF YEAST. 2C3 

forming at first around its edge, gradually increases and spreads till it 
meets in the centre, and the whole surface becomes covered with a 
white creamy foam. The bubbles of gas {carlonic acid) then rise and 
break in such numbers, that they emit a low hissing sound, and the 
white foam of yeast continues to increase in thickness, breaking 
into little pointed heaps, which become brownish on the surface and 
edges ; the yeast gradually thickening until it forms a tough, viscid 
crust." Although a portion of the yeast was spent in the operation, 
yet a much larger quantity has been produced from the nitrogenous 
matter of the grain in the solution. 

496. Appearance of Yeast— It is a Plant. — Yeast, as usually procured 
from the brewer, is a yellowish gray or fawn-colored frothy liquid, 
of a bitter taste, and which shrinks in a few hours into one-fourth 
the space it occupied at first. When fresh, it is in constant move- 
ment, and bubbles of gas escape from it. When dried it loses 70 per 
cent, of its weight, becomes solid, horny-looking, half-transparent, and 
breaks readily into gray or reddish fragments. The nature of yeast 
was for a long time matter of doubt and speculation, but the micro- 
scope has at length cleared up the question, and showed t?aat it is a 
true plant belonging to the Fungus tribe. Under a powerful magni- 
fier, it is seen to consist of numberless minute rounded or oval bodies, 
which are true vegetable cells. Each little globule consists of an en- 
veloping skin or membrane, containing a liquid within. Such cells 
are the minute agencies by which all vegetable growth is afliected. 
The leaves and pulpy parts of plants are built up of them, as a wall 
is built of bricks. All the numberless substances produced by plants, 
are generated within these little bodies. They grow or expand from 
the minutest microscopic points and seem to 
bud off from each other, as shown in Figs. 98 
and 99. The little grains from which they Cv^/t^"!) A'^^ 

spring or germinate are shown, and how they ,^,-v-vr>,^^,_r^ /^ 
multiply by budding. They are of amazing ''^^■^^'^^^tir^Y^^^ '^ 
mmuteness, a single cubic inch of yeast, free 
from adhering matter, containing as many 
as eleven hundred and fifty-two millions 
of them. In what manner yeast acts to 
decompose sugar is not kno^vn. The yeast 
is destroyed or expends itself in producing 
the effect, yet it furnishes none of its sub- Yeast coii?, showing' how thoy 
stance to join with the sugar, in producing ^;SiV'':^':^^ 
alcohol and carbonic acid. Liebig supposes ^'""""^ ^''*^''" i"te'"""". 
the effect to be dynamic^ tiiat is, produced by an impidse of force ; the 




264 CULINARY CHANGES OF ALIilENTAEY SUBSTANCES. 



motions of the atoms of the decomposing ferment, being communi- 
cated to the atoms of sugar, set these also in motion, by which the 
sugar structure is, as it were, jarred and shaken to pieces, its atoms 
falling into new arrangements and forming new substances. 

497. Domestic preparation of Yeast — Fowne's method. — But, as 
many have no access to breweries, it is desirable to know how 
to make yeast at home. If common wheaten flour be mixed 
with water to a thick paste, and 
exposed slightly covered, and 



Fig. 99. 



left to spontaneous change in a 



M 



moderately warm place, it will, @ >> (^ 
after the third day, begin to ©©^^^^^ Q 



"0^@ - 




emit a little gas, and to exhale 
an exceeding disagreeable sour 
odor. After the lapse of some 
time this smell disappears ; the 
gas evolved is greatly increased, 
and is accompanied with a dis- 
tinct agreeable vinous odor ; this 
will happen about the sixth or 
seventh day, and the substance 
is then in a state to excite fer- 
mentation. An infusion of crush- 
ed malt (wort) is then boiled 
with hops, and when cooled to 
90° or 100°, the altered dough, 
above described, after being 
thoroughly mixed with a little 
lukewarm water, is added to it, 
and the temperature kept up by ^,t£&'Sv?\Taifo'fg^^^^^^^^ 
placing the vessel in a warm situ- 
ation. After a few hours fermentation commences, and when that is 
complete, and the liquid clear, a large quantity of excellent yeast is 
formed at the bottom. 

498. Yeast from Potatoes.— Boil half a dozen potatoes in three or 
four quarts of Avater, with a couple of handfuls of hops placed in a 
bag. Mash the potatoes and mix Avith the water, adding and stirring 
in a little salt, molasses and flour, until it is of a battery consistence. 
Then mix in a couple of spoonfuls of active yeast. Place before the 
fire, when it will soon begin to ferment. In a cool place it may 
be kept for weeks. 



PROPERTIES AND ACTION OF YEAST. 265 

499. Action of Hops in Ycast-malting. — Hop-flowers contain about 8 
percent, of a brownish yellow bitter volatile oil, upon which its pecu- 
liar odor depends. The hop has been long knowm for its soporitic or 
sleep-producing properties, which are supposed to be duo to this 
volatile narcotic oil. When dry hop-flowers are beat, rubbed and 
sifted, they yield about 8 per cent, of fine yellow dust— an aromatic 
resin, which has an agreeable odor, and a bitter taste. When taken 
internally it has a soothing, tranquillizing, sleep-provoking influence. 
It is called lupulin. Hops also contain a considerable proportion of 
another strong bitter principle, which is said not to be narcotic. In 
brewing, the chief use of hops is to impart an agreeable bitterness to 
the beer, but it also has the efiect of arresting or checking fermenta- 
tion before all the sugar is converted into alcohol, and then prevent- 
ing the production of acid. It is also well-known that in the domestic 
preparation of yeast, hops serve to prevent the mixture from souring, 
though TioiD this is affected we cannot tell. 

500. Yeast preserved by drying. — The liquid, or active yeast, is liable 
to turn sour and spoil in warm weather, losing its properties and im- 
parting to bread a most disagreeable flavor. Drying has therefore 
been resorted to, as a means of preserving it. On a large scale, it is 
pressed in bags and dried at a gentle heat, until it loses two-thirds of 
its weight of water, leaving a granular or powdery substance, which, 
if packed and kept from the air and quite dry, may be preserved a 
long time. It is curious that mechanical injury kills or destroys yeast. 
Falls, bruises, a rough handling spoils it, so that great care is required 
to remove it from place to place. Liebig remarks that simple pressure 
diminishes the power of yeast to excite the vinous fermentation. 
Yeast is also preserved by dipping twigs in it and drying them in the 
air. Or it may be worked round with a whisk until it becomes 
thin, and then spread with a brush over a piece of clean wood and 
dried. Successive coats may be thus applied, until it becomes an inch 
or two in thickness. When thoroughly dried, it can be preserved in 
bottles or canisters. Yeast is also commonly preserved by adding to it 
maize meal, and making it into a dough which is wrought into cakes 
and dried. They may be kept for months and are ready for use at 
any time, by crumbling down and soaking a few hours in warm water. 
We add minuter directions for making yeast-cakes. Eub three ounces 
of fresh hops until they are separated, boil half an hour in a gallon of 
water, and strain the liquid through a fine sieve into an earthen vessel. 
While hot, stir in briskly 3^ lbs. of rye flour. Next day, thoroughly 
mix in 7 lbs. of Indian meal, forming a stiff" dough ; knead it well, roll 

12 



266 CULINAKT CHANGES OF ALIMENTARY SUBSTANCES. 

it out a third or half an incli tliick, cut iuto cakes and dry in the sun, 
turning every day and protecting from wet. If preserved perfectly 
from damp they Avill keep long. 

501. Bitterness of Yeast— how corrected. — Yeast is often so bitter as to 
communicate a most disagreeable taste to bread. This may be de- 
rived from an excess of hops. To rectify this, mix with the yeast a 
considerable quantity of water, and set it by to rest for some hours, 
when the thickest part will fall to the bottom. Pour off the water 
which will have extracted a part of the bitter principle, and use only 
the stiff portion that has fallen to the bottom. But yeast sometimes 
acquires a bitter taste from keeping, which is quite independent of that 
derived from the hops. One method of remedying this, consists in 
throwing into the yeast a few clean coals freshly taken from the fire, 
but allowed to cool a little on the surface. The operation appears to 
depend in principle upon the power of freshly burnt charcoal to ab- 
sorb gases and remove offensive odors (811). 

502. Acidity of Yeast — how corrected. — In country places, where it is 
customary to keep yeast for some time, and especially during the 
warmth of summer, it is very liable to sour. In such case, it may 
be restored to sweetness, by adding a little carbonate of soda or car- 
bonate of magnesia, only so much being used as may be necessary to 
neutralize the acidity. 

503. Dough raised by Yeast. — How fermentation lightens dough, has 
been shown (493). Yeast produces these changes promptly and effec- 
tually. It is mixed with a suitable portion of water, flour, and salt, 
to form a stiff batter, which is placed near the fire for an hour or two, 
covered with a cloth. This is called setting the sponge. An active fer- 
mentation is commenced, and the carbonic acid formed in the viscid 
mass, causes it to swell up to twice its original size. If not then quickly 
used iifalls^ tliat is, the accumulated gas within escapes, and the dough 
collapses. Yet after a time it may again rise, and even fall a second 
time and rise again. This, however, is not allowed. "When it has fully 
risen, much more flour is thoroughly kneaded with the sponge, and 
the dough is left for perhaps an hour and a half, when it rises again. 
It is then again kneaded and divided into pieces of the proper size foi 
loaves. The loaves should be moulded with care, as too much band- 
ling is apt to cause the escape of the enclosed gas, and make the 
bread heavy. 

504. Correction of Acidity in Dongh. — Dough is frequently sour 
from an acid condition of the flour. It may be in this condition from 
a sour state of the yeast, or the fermentation may be so feeble as to 



KAISING BREAD WITHOUT FERMENTATION. 207 

produce acid (476), or it may be too active and rapid, if too much or 
too strong yeast has been used ; or in hot weather when the dough is 
liable to sour by running into the acetous fermentation. If the diffi- 
culty is too sluggish a change, it should be hastened by securing the 
most favorable warmth. If, on the contrary, it is too violent, it may be 
checked by uncovering the dough, and exposing it to the air in a cool 
place. If the dough be ali'eady sour, it may be sweetened by alkaline 
substances. Carbonate of soda will answer this purpose. Carbonate 
of ammonia is perhaps better, as it is a volatile salt, and is raised in 
vapor and expelled by the heat of the oven (510). If too much be used, 
a portion of the excess is driven off by the heat, and in escaping assists 
in making the bread lighter. Caution should, however, be employed 
to use no more alkali than is really necessary to neutralize the acid. 
When the acidity is but slight, it may be rectified by simply kneading 
the dough with the fingers moistened with an alkaline solution. 

505. The Sngar of Flonr all decomposed in Dough. — It is at the ex- 
pense of sugar destroyed that fermented bread is raised, but how m^icJi 
sugar is thus decomposed is variously stated, and depends upon the 
activity and continuance of fermentation. Experiments would seem 
to show, that all the sugar present is rarely, if ever, destroyed. 
The raised dough and bread both contain sugar, often nearly as much 
as the flour before it was used. This is explained by remembering 
that one of the effects of fermentation is to change starch to sugar. 

506. How mnch Alcohol is produced in Bread. — Of course the quantity 
of alcohol and carbonic acid generated in bread is in exact proportion 
to the amount of sugar destroyed, which, as we have said, is by no 
means constant. In an experiment, a pound of bread occupied a space 
of GO cubic inches, 26 of which were solid bread, and 34, cell-cavi- 
ties ; consequently 34 cubic inches of carbonic acid of the heat of the 
oven were generated to raise it, which implied the production of about 
15 grains of alcohol, or less than one-quarter of one per cent, of the 
weight of bread. It has been attempted to save this alcohol, which 
is vaporized and driven off into the air by the baking heat, but the 
product obtained was found to be so small as not to pay cost. It is 
also a current statement, that alcohol exists in the bread, contributing 
to its nutritive qualities. "We have never found it there, and never 
saw a chemical analysis of bread that enumerated it as a constituent. 

4. Eaisikg Bread without Fermentation. 

507. Objections to raising by Ferment. — Two or three objections have 
been urged against raising bread by fermentation. Firat^ the loss of 



208 CULINARY CHANGES OF ALIMENTARY SUBSTANCES. 

a portion of the sugar of the flour which is decomposed ; this loss, how- 
ever, is trifling, and the objection futile. It is said, secondly, that aa 
a destruction or incipient rotting process has been established in the 
dough, bread made from it cannot be healthful. This is onlj fancy, 
experience i.s wanting to show that well-made fermented bread is in- 
jurious. Thirdly, it is said that the fermenting process is not only 
uncertain, but slow, and requires more time than it is often convenient 
to allow. There is such force in this latter objection, that means have 
been sought to replace fermentation by some quicker and readier 
method of raising the dough. 

508. How it is done witiiont Ferment. — As the lightening and expan- 
sion of the dough are caused by gas generated within it, it would seem 
that we may adopt any means to produce such a result. It is com- 
monly done in two ways ; either by mixing chemical substances 
with the flour, which, when brought into contact and wet, act 
upon each other so as to set free a gas, or by introducing into the 
dough a volatile solid substance, which, by the heat of baking, rises 
into the state of gas. In the first case, substances are used which set 
free carbonic acid ; in the second case, a compound of ammonia. 

509. Raising Bread with Chemical Substances. — Bicarbonate of soda and 
hydrochloric acid are used for raising bread. The soda is mixed inti- 
mately with the flour, and the acid is added to the water requisite to 
form dough. Peeeira indicates the following proportions : 

Flour 1 lb. 

Bicarbonate of soda 40 grains. 

Cold water, or any liquid necessary \ pint. 

Hydrochloric acid 50 drops. 

The soda and flour being mixed, the acidulated water is added gradu- 
ally, with rapid stirring, so as to mix speedily. Divide into two loaves, 
and put into a hot oven immediately. The acid combining with the 
soda, sets free its carbonic acid, which distends the dough. Both the 
acid and the alkali disappear, are destroyed, and the new sub- 
stance formed by their union is chloride of sodium, or common salt ; 
so that this means of raising bread answers also to salt it. If the in- 
gredients be pure, the proportions proper, and the mixture perfect, no 
other substance will remain in the bread. If the acid be in excess, there 
will be sourness; and if there be too much alkali, or if it be not en- 
tirely neutralized, unsightly yellow stains in the bread crumb will be 
apparent, accompanied by the peculiar, hot, bitter, alkaline taste, and 
various injurious effects. The changes that take place are thus shown. 
We begin with — 



RAISING BREAD WITHOUT FERMENTATION. 269 



BiCAKBONATK OF soda; ^ ^ ^ 

(sohd,) and r .^^ ' 

Hydrochloric acid: I ^„„„u 



Carbonic acid; 

(ffOS,) 

Water ; 

(liquid,) and 
Common salt ; 

{solid.) 



Breaa is also raised with soda powders ; — tartaric acid, and bicar- 
bonate of soda, whicli are the active ingredients in effervescing draughts. 
The changes are these 

Bicarbonate of soda; ') -,„.j„„„ C Carbonic acid; 

{solid,) and ( '^^f,, the \ (^""'^ ^"^ 

Tartaric acid; I .^ ^, ) Tartrate of soda; 

{solid,) 3 ^^'■'S^' ( {solid.) 

Cream of tartar, consisting of tartaric acid combined with and partly 
nentralized by potash, is also used with soda, one being mixed with 
flour, and the other dissolved in water. Double the quantity of cream 
of tartar to soda is commonly used, but of tartaric acid only an equal, 
or slightly less quantity. In these cases tartrate of soda is formed in 
the bread, which, in its action upon the system, is like cream of tartar 
— gently aperient. Preparations which are known as egg-2)oicder, 
'baMng-poicder, and custard-powders., consist of bicarbonate of soda and 
tartaric acid, mixed with wheat flour or starch, and colored yellow 
with turmeric, or even poisonous chromate of lead. The difliculty with 
these powders, is to get them in perfect neutralizing proportions. 
This may be ascertained by dissolving them in water ; the mixture 
should be neutral to the taste, and produce no effervescence by 
adding either alkali or acid. Sour milk, or buttermilk, are often used 
with soda or saleratus. In these cases the lactic acid tliey contain 
combines with the alkali, forming lactate of soda, or potash, and set- 
ting carbonic acid free, wliich lightens the dough, just as in all the 
other instances. 

510. Sesqniearbonatc of Ammonia. — The perfect theoretic conditions 
of raising bread without ferment would be, to find a solid substance 
which could be introduced into the flour, but which would entirely es- 
cape as a gas during baking, raising the bread, and leaving no trace of 
its presence. Carbonate of ammonia complies with the first of these 
conditions ; it is a solid which, under the influence of heat, is decom- 
posed entirely into gases. Thus — 



Sesquicarbonate of ) • , , . 
Ammonia; ( m baking 

'Mid,) S P"""^"^^^' 



Ammonia ; 

Bicarbonate or 
Ammonia ; 

Carbonic acid , 
{gas.) 



270 CULINARY CHANGES OF ALIMENTARY SUBSTANCES* 

Yet practically these gases do uot all escape in baking ; a portion of 
them is apt to remain, communicating a disagreeable hartshorn flavor. 
All these methods have one common and serious disadvantage — the 
gas is set free too suddenly to produce the best effect. Alum and car- 
bonate of ammonia are sometimes used ; they act more slowly, but 
leave an unwholesome residue of alumina and sulphate of ammonia in 
the bread. 

511. Important Caation in reference to tbe Chemicals used. — The class 
of substances thus introduced in the bread are not nutritive but me- 
dicinal, and exert a disturbing action upon the healthy organism. 
And although their occasional and cautious employment may perhaps 
be tolerated, on the ground of convenience, yet we consider their ha- 
bitual use as highly injudicious and unwise. This is the best that can 
be said of the chemical substances used to raise bread, even when 
pure, but as commonly obtained they are apt to be contaminated with 
impurities more objectionable still. For example, the commercial mu- 
riatic acid which is commonly employed along with bicarbonate of 
soda, is always most impure — often containing chlorine, chloride of 
iron, sulphurous acid, and even arsenic, so that the chemist never uses 
it without a tedious process of purification for his purposes, which are 
of far less importance than its employment in diet. While common 
commercial hydrochloric acid sells for 3 cents per pound wholesale, 
the purified article is sold for 35. Tartaric acid is apt to contain lime, 
and is frequently adulterated with cream of tartar, which is sold at 
half the price, and greatly reduces its eflBcacy ; while cream of tar- 
tar is variously mixed witli alum, chalk, bisulphate of potash, tartrate 
of lime, and even sand. Sesquicarbonate of ammonia is liable by ex- 
posure to air to lose a portion of its ammonia. It is hence seen that 
the substances we employ are not only liable to injure by ingredients 
which they may conceal, but that their irregular composition must 
often more or less defeat the end for which they are intended. "We 
may suggest that, in the absence of tests, the best practical defence is 
to purchase these materials of the druggist rather than the grocer. If 
soda is desired, call for the Mcarloiiate of soda ; it contains a double 
charge of carbonic acid, and is purest. Soda-saleratus is only the 
crude, impure carbonate — soda-ash. The cream of tartar should appear 
white and pure, and not of a yellowish tinge (698). 

512. Raising Dongli with Oily Substances and Eggs. — If dough be mixed 
with butter or lard, rolled out into a thin sheet, and covered with a 
thin layer of the oily matter, then folded, rolled and recoated from 2 
to 10 times, and the sheet thus produced be submitted to the oven, the 



ALTERATIONS PRODUCED IN BAKING BREAD, 2Vl 

heat causes the disengagement of elastic vapor from the water and 
fatty matter, which, being diffused between the numerous layers of 
dough, causes them to swell up, producing the flaky or puffy appearance 
which is seen in ^9«s^?'y. This kind of lightness must not be confound- 
ed with that produced by the other methods described ; for, although 
the layers are partially separated, yet the substance of each stratum 
is dense and hard of digestion. The albumen of eggs, when smartly 
beaten, becomes frothy and swells, by entangling much air in its 
meshes. If then mixed with -{lough, it conveys with it air bubbles, 
which are expanded in baking. From its glairy, tenacious consistence 
when mixed with dough or pudding, it encloses globiJes of gas or 
steam, which are generated by fermentation or heat. In this way eggs 
contribute to the lightness of baked articles. 

513. Raising Giogerlireadt — Gingerbread usually contains so much 
molasses that it cannot be fermented by yeast. But the molasses is of 
itself always acidulous, and takes effect upon the saleratus, setting 
free carbonic acid gas. Sour milk, buttermilk, and cream, are also 
used, which act in the same way upon the carbonate of soda or potash, 
and thus inflate the dough. Dr. Oolquhoun has found that carbonate 
of magnesia and tartaric acid may replace the saleratus (and alum 
also, which is sometimes used), affording a gingerbread more agreeable 
and wholesome than the common. His proportions are, 1 lb. of flour, 
I oz. carbonate of magnesia, | oz. of tartaric acid, with the requisite 
molasses, butter, and aromatics. 

5. Alterations Peoduoed m Baking Beead. 

514. Temperature of the Oven.— Bread is usually baked by heat radi- 
ated or conducted from the brick walls or iron plates of which ovens 
are made. The oven should be so constructed that the heat may be 
equal in its different parts, and remain constant for a considerable 
time. If the heat be insufficient, the bread will be soft, wet, and 
pasty ; if on the other hand the heat be too great at first, a thick, 
burnt crust is produced, forming a non-conducting carbonaceous cov- 
ering to the loaf, which prevents the heat from penetrating to the 
interior. Hence a burnt outside is often accompanied by half-raw 
dough within. If, however, the temperature be proper, the heat 
passes to the interior of the loaf and produces the necessary changes 
before the outside becomes thickly crusted. If we cut open a well 
baked loaf, immediately from the oven, and bury the bulb of a ther- 
mometer in the crumb, it will rise to 212°. This heat is sufficient to 



272 CULINARY CHANGES OF ALIMENTAET SUBSTANCES. 

cany on the inner chemical changes of baking, and it is obvious that 
the heat cannot rise above this point so long as the loaf continues 
moist (65.) Bread might be baked at a temperature of 212° (by 
steam), but then it would lack that indispensable part, the crust. The 
baking temperature of the oven ranges from 350° to 450° or 500°, and 
bakers have various means of judging about it. If fresh flour strewn 
upon the oven bottom turns brown, the heat is right, if it chars or 
turns black, the heat is too great. 

515. Heat causes a loss of Weight. — The loaf loses a portion of its 
weight by evaporation. The quantity thus lost depends chiefly upon 
the size and form of the loaf. If it be small or thin, it will part with 
more water in proportion than if of cubical shape. Something de- 
pends upon the quality of the flour and tlie consistence of the dougli. 
Various experiments would seem to show that bread parts with from 
one-sixth to one-tenth of its weight in baking. In those places where 
bread is required by law to be of a certain weight, this loss must be 
calculated upon and a proportionate amount of additional flour used. 
Peechtl states from experiment that loaves which, after baking and 
drying, weigh one pound, require that an extra weight be taken, in 
dough, of six ounces ; if the loaves are to weigh three pounds, twelve 
ounces additional must be taken, and if six pounds, sixteen ounces. 

516. How Heat enlarges the Loaf. — When the loaf is exposed to the 
heat of the oven, it swells to about twice its size. This is owing to 
the expansion of the carbonic acid gas contained in its porous spaces, 
the convej'sion of water into steam, and the vaporizing of alcohol, 
which also rises into the gaseous form and is driven off, as is shown 
by the spirituous odor yielded in the baking process. 

517. Chemical Changes in prodncing the Crnst. — The heat of the oven 
falling upon the surface of the loaf causes first the rapid evaporation 
of its water, and then begins to produce a disorganization of the 
dough. The starch-grains are ruptured (530) and its substance con- 
verted into gum ; as the roasting continues chemical decomposition 
goes on, and organic matter is produced of a brown color, an agreeable 
bitter taste, and soluble in water, which has received the name of 
assamar. The formation of hard crusts on the loaf may be prevented 
by baking it in a covered tin, or, it is said, by rubbing a little melted 
lard over it after it is shaj^ed and before it is set down to rise. 

518. Chemical Changes in prodncing the Cramb. — As the temperature 
within the loaf does not rise above 212°, no changes can go on there 
except such as are produced by the heat of the aqueous vapor. This 
b sufficient to stop the fermentation, • destroy the bitter principle of 



ALTERATIONS PKODUCED IN BAKING BREAD. 273 

the yeast, and kill the yeast plant. In haking ahout one-fonrteenth of 
the starch is converted into gum, the rest is not chemically altered, as 
may be shown by moistening a httle bread-crumb and touching it with 
solution of iodine, when the blue color will prove the presence of 
starch. The gluten, although not decomposed, is disunited, losing its 
tough, adhesive qualities. The gluten and starch-paste are intimately 
mixed, but they do not unite to form a chemical compound. 

619. Sloistore contained in Bread. — In newly-baked bread the crust 
is dry and crisp, while the crumb is soft and moist, but after a short 
time this condition of things is quite reversed. The brown products 
of the roasting process attract moisture and the crust gets daily softer, 
while the crumb becomes dry. Bread, two or three days old, loses 
its softness, becoming hard and crumbly. But this apparent dry- 
ness is not caused by evaporation or loss of water, for it may be 
shown by careful weighing that stale bread contains almost exactly 
the same proportion of water as new bread that has become com- 
pletely cold. The change to dryness seems to be one of combination 
going on among the atoms of water and bread. That the moisture 
has only passed into a state of concealment may be shoAvn by exposing 
a stale loaf in a closely covered tin for half-an-hour to a boiling heat, 
when it will again have the appearance of new bread. The quantity 
of water which weU-baked wheaten bread contains amounts, on an 
average, to about 45 per cent. The bread we eat is, therefore, n'^arly 
one-half water. It is, in fact, both meat and drink together. One of 
the reasons why bread retains so much water is, that during the 
baking a portion of the starch is converted into gum, which holds 
water more strongly than starch does. A second is, that the gluten 
of flour when once thoroughly wet is very difficult to dry again, and 
that it forms a tenacious coating round every little hollow cell in the 
bread, which coating does not readily allow the gas contained in the 
cell to escape, or the water to dry up and pass off in vapor ; and a 
third reason is, that the dry crust which forms round the bread in 
baking is nearly impervious to water, and, like the skin of the potato 
we bake in the oven or in the hot cinders, prevents the moisture from 
escaping. — (Johnston.) 

520. Qnalitics of Good Bread. — In baking bread, it is desirable to 
avoid the evils of hardness on the one hand and pastiness on the other, 
nor should it be sour, dense, or heavy. It should be thoroughly and 
uniformly kneaded, so that the carbonic acid will not be liberated in 
excess in any one place, forming large hollows and detaching the 
crumb from tht crust. The vesicles should be numerous, small, and 
12* 



274 CULINARY CHANGES OF ALIMENTARY SUBSTANCES. 

eqnally disseminated ; nor should the crust be bitter and black, but oi 
an aromatic agreeable flavor. " If the yeast be so diffused throughout 
the whole mass as that a suitable portion of it will act on each and 
every particle of the saccharine matter at the same time, and if the 
dough be of such consistency and temperature as not to admit of too 
rapid a fermentation, then each minute portion of saccharine matter 
throughout the whole mass will, in the process of fermentation, pro- 
duce its little volume of air, which will form its little cell, about 
the size of a pin's head and smaller, and this will take place so nearly 
at the same time in every part of the dough, that the whole will bo 
raised and made as light as a sponge before the acetous fermentation 
takes place in any part. And then, if it be properly moulded and baked, 
it will make the most beautiful and delicious bread, perfectly light and 
sweet, without the use of any alkali, and with all the gluten and nearly 
all the starch of the meal remaining unchanged by fermentation." — 
(Geaiiam.) 

6. Intluexce of Foreign Substances upon Beead. 

521. Common Salt, Alum, kc, — It has been found that certain mineral 
substances influence in a remarkable degree the aspect and properties 
of bread, causing that made of inferior flour to resemble, in appear- 
ance, bread made from the best quality. Common salt produces this 
effect in a decided degree. It whitens the bread and causes it to 
absorb and retain a larger amount of water than the flour would 
otherwise hold. In consequence of this influence and under cover of 
the fact, that salt is a generally admitted element of diet, it is often 
introduced into bread more freely than is consistent with health (G97). 
Alum has exactly the same effect on bread as common salt, but in a 
much more marked degree. A small quantity of it will bring up a 
bad flour to the whiteness of the best sort, and will enable it to hold 
an extra dose of water. It is much used for this purpose, and the 
baker who employs it not only practises upon the consumer a double 
imposition, but drugs him with a highly injurious mineral into tho 
bargain. Mitchell detected in ten four-pound loaves 819 grains of 
alum, the quantity in each loaf ranging from 34 to 116 grains. Sul- 
phate of copper (blue vitriol), in exceedingly minute proportions, 
exerts a striking influence upon bread in the same manner as alum. 
Carhonate of magnesia has a similar eff'ect, and its use in so large 
quantities as from 20 to 40 grains to the pound of flour has been re- 
commended on scientific authority.* This substance has been also 
• Dr. C. Davy. 



iJSTLUENCE OF FOKEIGN SUBSTANCES UPON BREAD. 275 

recommended for correcting acidity in yeast, dough, &c., instead of 
soda, and because it is less po-vverfully alkaline. But from its diffi- 
cultly soluble earthy nature, it tends to accumulate in the system in 
the highly objectionable shape of concretions and deposits. 

522. Liebig recommends Lime-water in Bread. — However it is to be 
lamented, it is nevertheless a fact, that enormous quantities of flour, 
more or less deteriorated, are purchased in the markets of this country ; 
and if there be any method of improving its condition by means that 
are not essentially injurious, they are certainly most desirable. Indeed, 
it is well known that flour is injured by time alcne, so that freshly 
ground flower is always more prized than that which is several months 
old. The scientific reason is apparent. Vegetable gluten in contact 
with water becomes chemically changed, and loses its peculiar tough 
elastic properties. As these are essential to bread-making, flour that 
has been altered in this way necessarily makes a bad dough. Now, 
flour is in a high degree a water-absorbing substance, so much so tha't 
it attracts and combines with the moisture of the air, and is thus 
injured. This can only be avoided by artificial drying and protecting 
thoroughly from the air. The effect of the substances noticed in the 
previous paragraph is to combine with the gluten thus partially 
changed, and in a measure to restore its lost properties. Upon inves- 
tigating this subject, Liebio found that lime-water is capable of pro- 
ducing this effect, and thus of greatly improving old, or low grade 
flour. 

523. How Lime-water Bread is prepared, — To make lime-water 
chemists usually employ water that has been distilled; very pure 
soft water, as clean rain water, may, however, be used. Mix a quarter 
of a pound of slacked lime in a gallon of such cold water in stoppered 
bottles or vessels kept tight from the air. The mass of the lime falls 
to the bottom, leaving the liquid above, which has dissolved l-GOOth 
its weight of lime, clear and transparent. This is to be poured oft 
when required for use and replaced by pure water. Liebig recom- 
mends 5 lbs. or pints of lime-water to every 19 lbs. of flour, although 
this quantity of lime-water does not sufiice for mixing the bread, 
and of course common water must be added, as much as is requisite. 
" If the lime-water be mixed with flour intended for the dough, and 
then the yeast added, fermentation progresses in the same manner as 
in the absence of lime-water. If at the proper time more flour bo 
added to the risen or fermented dough, and the whole formed into 
loaves and baked as usual, a sweet, beautiful, fine-grained elastic 
bread is obtained of exquisite taste, which is preferred by all who have 



27G CULINARY CHANGES OF ALIMENTARY SUBSTANCES. 

eaten it for any length of time to any other." — (LiEnio.) The use of 
lime-water removes all acidity from the dough, and also somewhat 
augments the proportion of Avater absorbed. 

524. Its Physiological claims. — The quantity of lime introduced into 
the system by the use of this bread, is by no means large. A pound 
of lime-water suffices for 4 lbs. of flour, which with the common water 
added, yields 6 lbs. of bread ; and as the pound of lime-water contains 
but l-600th of lime, Avith this artificially added the cereal grains 
still contain less of it than peas and beans. Indeed, Liebig hais sug- 
gested that experience may yet prove the cereal grains to be incapable 
of perfect nutrition, on account of their small proportion of the bone 
forming element. 

525. Differcat kinds of Bread. — Rice flour added to wheaten flour 
enables it to take up an increased quantity of water. Boiled and 
mashed potatoes mixed v/ith the dough cause the bread to retain 
moisture, and prevent it from drying and crumbling. Rye makes a 
dark-colored bread, and is capable of being fermented and raised 'u 
the same manner as wheat. It retains its freshness and moisture 
longer than Avheat, An admixture of rye flour, with that of wheat, 
decidedly improves the latter in this respect. India?i corn bread is 
much used in this country. Mixed Avith wheat and rye, a dough is 
produced capable of fermentation, but pure maize meal cannot be fer- 
mented so as to fonn a light bread. Its gluten lacks the tenacious 
quality necessary to produce the regular cell-structure. It is most 
commonly used in the form of cakes, made to a certain degree light 
by eggs or sour milk and saleratus, and is generally eaten warm. 
Indian corn is ground into meal of various degrees of coarseness, but 
is never made so fine as wheaten flour. Bread or cakes from maize 
require a considerably longer time to be acted upon by heat in the 
baking process than wheat or rye. If ground wheat be unbolted, that 
is, if its bran be not sepai-ated, wheat meal or Graham flour results, from 
which Graham or dyspepsia bread is produced. It is made in the same 
general way as other wheaten bread, but requires a little peculiar man- 
agement. Upon this point Mr. Geaham remarks : " The wheat meal, 
and especially if it is ground coarsely, swells considerably in the 
dough, and therefore the dough should not at first be made quite so 
stiff as that made of superfine flour; and when it -is raised, if it is 
found too soft to mould well, a little more meal may be added." It 
should be remarked that dough made of wheat meal will take on the 
acetous fermentation, or become sour sooner than that made of fine 
flour. It requires a hotter oven, and to be baked longer. Puddings 



VEGETABLE POODS CHANGED BY BOILING. 2'?'? 

In which floor is an ingredient are changed by the baking process in 
the same way as bread. They are usually mixed with milk instead 
of water, and made thinner than dough. Yeast is not used to raise 
them, eggs being commonly employed for this purpose, and sometimes 
other substances. 

520. White and Brown Bread— A new French Plan. — M. Motjkies, of 
Paris, has announced some new views of bread making, theoretic and 
practical, upon which a commission of the French Academy has just 
reported favorably. He claims the discovery of a nitrogenous sub- 
stance called cereaUne, which is a very active feiment, rendering 
starch soluble, altering gluten to a brown substance, and actively pro- 
ducing lactic acid instead of carbonic acid and alcohol. It resides 
near the surface of the wheat-grain, so that in grinding, it is nearly all 
separated in the bran, leaving but little in the white flour. M. Mou- 
EiEs states that in bread made from unbolted flour, the tendency to 
sourness, the softness, crumbliness, and want of firmness of the crumb, 
and the hroioi color also of the bread, are due to cereaUne. He says 
cerealine ferment will make a brown bread of the whitest flour, 
whereas, if it be neutralized, a white tread can te made from a darh 
flour containing Iran. He grinds wheat so as to separate it into about 
Y4 per cent, of fine flour, 16 of brown meal, and 10 of bran. The 
brown meal is then so acted on by yeast as to neutralize the cerealine. 
The product in a liquid form is used to mix white flour into dough, 
which is baked as usual. The claims of this method are, a larger 
economy of ground products, making a white bread from dark mate- 
rials, preventing the liability to acidity, and a yield of the finest, 
lightest, and sweetest bread, comprising the largest portion of farina- 
ceous materials. 

v. — Vegetable Foods changed by BoiLrjrG. 

527. Its General Effects. — Boiling differs from baking in several re- 
spects. First., the heat never rises above the boiling point, and the 
changes of course are such only as may be produced by that tempera- 
ture. Second^ the food is surrounded by a powerful solvent, which 
more or less completely extracts certain constituents of the food. Veg- 
etable acids, sugar, gum existing in the organic matter, and gum 
formed from starch, with vegetable albumen, are all soluble in water, 
and by boiling are partially removed. The tougher parts are made 
tender, the hard parts softened, and the connections of the fibres and 
tissues loosened, so as to be more readily masticated, more easily pen- 
etrated by the saliva and juices of the stomach, and hence more 



278 CULINAET CHANGES OF ALIM^ilNTARY SUBSTANCES. 

promptly and perfectly digested. Perhaps we inay here most con- 
veniently consider the specific eflects of heat upon the chief constitu- 
ents of which vegetahle foods are composed. 

528. Changes of Woody Fibre. — A constituent more or less abundant 
of all vegetable substances is woody fibre. We find it in the husk or 
bran of grains, the membrane covering beans and peas, the vessels of 
leaves and leaf-stalks, the skin of potatoes, the peel and core of apples 
and pears, the kernels of nuts, and the peel of cucumbers, melons, «fec., 
&c. "We are hardly justified in ranking woody fibre, as Pereiea has 
done, among aliments. Indeed, he remarks, "although I have placed 
ligneous matter among the alimentary principles, yet I confess I am 
by no means satisfied that it is capable of yielding nutriment to man." 
Yet it is important to understand how it may be affected by the heat 
of culinary operations. Boiling in water does not dissolve it ; but 
by dissolving various substances with which it is associated, it only 
renders it the more pure. Yet woody fibre seems capable, by the joint 
action of heat and chemical agencies, of being converted into nutritive 
matter. If old linen or cotton rags, paper, or fine sawdust, be boiled 
in a strong solution of alkali, or moistened with pretty strong sulphu- 
ric acid, the woody substance is changed, being converted first into 
gum or dextrin, and then into grape sugar. By such modes of treat- 
ment old rags may be made to yield more than their weight of sugar. 
But weak solutions of acid or alkali do not produce any such efl:ect. 
Nor will strong vinegar. "We may therefore assume that woody fibre 
remains totally unchanged by exposure to culinary agencies and ope- 
rations. Professor Autexrieth, of Tubingen, announced some years 
since, a method of preparing bread from wood-powder or wood-flour, 
which was changed into nutritive matter by successive heatings in an 
oven. We are not aware that his experiments have been confirmed, 
while it is suspected that whatever nutritive value his bread may have 
possessed, was due to starch associated with the wood. 

529. Changes of Sugar. — Sugar, dissolved in cold water, or boiled 
to a sirup, has very difterent properties, as is well known to those 
who feed it to bees in Avinter. In the first case, the warmth of the 
hive will dry up the water and leave the sugar in hard crystals which 
the bees cannot take ; but by boiling, the water and sugar become so 
intimately united that.the mixture does not become dry, but retains 
the consistence of sirup. If melted sugar be kept for some time at 
350°, it loses the property of crystallizing when redissolved in water, 
its properties being in some way deeply altered. If dry sugar be 
lieated to a little above 400°, it loses the sugar taste and becomes not 



VEGETABLE FOODS CHANGED BY BOILING. 



279 



Fig. 100. 




only very soluble in water, but also very absorbent of it {deliquescent)^ 
turns of a deep brown color, and is used to stain liquids of a dai'k red, 
or wine color, under the name of caramel. Sugar itself is slightly 
acid, and forms compounds with bases which are of a salt nature, and 
known as saecTiarates. Caramel is more decidedly acid, and if the 
sugar be heated still higher it is converted into still stronger acid pro- 
ducts with inflammable gases. 

530. Breaking np of the Starch Grains. — The structure of starch grains 
has been described (384). They consist of layers or coats arranged 
concentrically around a point called the hilum. If 
one of these grains be strongly compressed between 
two plates of glass it breaks apart into several pieces, 
as seen in Fig. 100, and all the planes of rupture 
generally pass through the hilum as if the substance 
were less resistent at that point. But under the joint 
action of heat and water, the grains break up diifer- 
ently. Their membranes are torn apart, or exfoliated 
by internal swelling, as shown in Fig. 101. 

531. Changes of Starch. — Starch is but slightly acted fhronf Mts hTium.^ 
upon by cold water. When heated with water it 

does not dissolve ; but the grains swell, forming a viscid mucilaginous 
mass, a kind of stiff, half opaque jelly. When starch is diluted with 
twelve or fifteen times its weight of water, 
the temperature of which is slowly raised, 
all the grains burst on approaching the 
boiling point, and swell to such a degree as 
to occupy nearly the whole volume of the 
liquid, forming a gelatinous paste. If a 
pint of hot water be poured on a table- 
spoonful of arrow-root starch, it imme- 
diately loses its whitenes and opacity, be- 
comes transparent, and the entire matter 

passes into the condition of a thick jelly. If a little of this be diffused 
through cold Avater and examined with the microscope, it will be seen 
that the starch grains are greatly altered. They have increased to 
twenty or thirty times their original size ; the concentric lines are 
obliterated (384) ; the membrane of the grain is ruptured, and its inte- 
rior matter has escaped. A cold jelly of starch and water, left to stand, 
either closed or exposed to the air, gradually changes, first into gum 
(dextrin), and then into sugar. The process, however, is slow, and 
months must elapse before the whole of the starch is thus transformed. 



Fig. 101. 




Starch grain ruptured by boil- 



280 CULINARY CHANGES OP AXIMENTAEY SUBSTANCES. 




By being boiled ia -water for a considerable time, it undergoes the 
same change, and if the water be acidulous the change is quickened. 
When dry starch is gradually heated to a temperature not exceeding 
300°, it slowly changes, acquires a yellow or brownish tint, and be- 
comes entirely soluble in cold water. It is changed to dextrin or 
gum (British gum). 

532. How Potatoes arc changed by Cooting. — By referring to the 
statement of the composition of potatoes (461), we shall notice that 
a pound contains about three-quarters of a pound of watery juice, to 
two ounces, or two and a half, of starch. When examined by the 

Fig. 102. microscope, the tissue cf the potato is found 

to consist of a mass of cells, containing starch 
grains. Each cell contains some 10 or 12 
grains, loosely situated, as shown in Fig. 102, 
and surrounded by the potato juice, which 
contains albumen. If potatoes be of good 
quality, they boil dry, or mealy^ as it is term- 
ed. But their water or juice does not sepa- 
rate, or boil out. It is absorbed by the starch 
Starcli grains of potato before grains, Avhich form a compound with it, and 
°' swell up so as completely to fill, and even 

burst the cells, as seen in Fig. 103. The albumen at the same time 
coagulates, so as to form irregular fibres, which are seen among the 
starch grains. When the juice of the potato is 
only partially absorbed by the starch, it is said to be 
watery, waxy, or doughy. Potatoes by boiling in 
water do not form a jelly, like common starch, be- 
cause the starch grains in the tubers are protected, 
partly by the coats of the cells in which they are 
contained, and partly by the coagulated albumen. 
" Potatoes steamed or roasted — or if boiled, mash- 
ed so as to extract all hard lumps, are in the best 
condition for digestion. Frying them, toasting 
Starch ^ains of potato them, baking them, or browning the surface, dries 
er o ing. ^^^ ^^^^ starch into a hard, half-charcoally mass, 
which, except in most powerful stomachs, must act as a foreign body." 

533. Qcality of the Water for Culinary Purposes. — Soft water, or that 
which is free from dissolved mineral matter, makes its way into, or is 
imbibed by organized tissues, with much more readiness and facility 
than hard water. It also exerts a more powerful solvent or extractive 
action, and thus is a better vehicle for conveying alimentary sub- 



Fio. 103. 




HOW COOKING CHANGES MEAT. 281 

stances into the living system. In culinary operations where the 
object is to soften the texture of animal and vegetable niattfjr, or to 
extract from it and pi-esent in a liquid form some of its valuable parts, 
as in making soups, broths, stews, or infusions, as of tea or coffee, soft 
water is the best. But there are cases in which the solvent action of 
soft water is too great, as sometimes upon green vegetables, which it 
makes too tender, destroying the firmness that is essential to the 
preservation of their juices, which are dissolved and extracted, making 
the substance proportionately tasteless. In those cases, therefore, 
when we do not desire to dissolve out the contents of a sti'ucture, but 
to preserve it firm and entire, hard water is better than soft. To pre- 
vent this over-dissolving action, common salt is often added to soft 
water, which hardens it. This fact also explains why it is impossible 
to correct and restore the flavor in vegetables that have been boiled 
in soft water by afterwards salting tliem. It is weU known that peas 
and beans do not boil soft in hard water. This is owing to the effect 
which salts of lime, especially the sulphate or gypsum, exert in hard- 
ening or coagulating casein which abounds in these seeds. Onions 
furnish a good example of the influence of quality in water. If boiled 
in pure soft water, they are almost entirely destitute of taste ; though 
Avhen cooked in salted water, they possess in addition to the pleasant 
saline taste, a peculiar sweetness, and a strong aroma ; and they also 
contain more soluble matter than when cooked in pure water. The 
salt hinders the solution and evaporation of the soluble and flavoring 
principles. 

8. How Cooking changes Meat. 

534. Action of Heat npon the Constituents of Flesh.. — If the pure fibrin 
of meat is exposed to a moderate heat, it parts with a large portion of 
its water, w^hich it held like a sponge, and loses the power of taking 
it up again. It consequently shrivels and shrinks. If the heat be 
carried high, further decomposition and charring take place. The effect 
of boiling upon fibrin, is not to make it more tender, but to increase its 
hardness and toughness. A low degree of heat changes liquid allumen 
to the solid condition ; altering remarkably all its physical properties. 
It neither dissolves in water, hot nor cold, and is impenetrable to it. 
If diffused through one or two hundred times its weight of water, it 
coagulates, forming fine fibrous meshes throughout the liquid suflicient 
to entangle any mechanical substances that may be floating in it, and 
bring them to the surface or carry them to the bottom. In this way 
albumen is used as a clarifying agent. If its proportion be much 



282 CULINARY CUANGES OF ALIMENTARY SUBSTANCES. 

larger, the entire water may combine with it and pass into the solid 
state. The egg, for example, contains 74 per cent, of water and 10 of 
oil, yet its contents are all solidified by boiling through the action of 
14 per cent, of pure albumen. Fat is liquefied, of course, by the action 
of heat, and at a high temperature it is resolved into various acid and 
acrid bodies. The eifect of heat upon flesh in the mass, has been in 
vestigated by Liebig, with his usual acuteness and with highly inter- 
esting and practical results. 

535. Properties of the Liqaid and Solid parts of Flesh. — When mus- 
cular flesh or lean meat is chopped fine, and steeped or leached with 
cold water, there remains a solid residue consisting of the muscular 
fibres, tissues, vessels, &c. If this be boiled, it is tasteless, or indeed 
slightly nauseating ; it cannot be masticated, and even dogs reject it. 
All the savory constituents of the flesh were contained in its juice ; 
and were entirely removed by cold water. The watery infusion thus 
obtained, is tinged red by some of the coloring matter of the blood. 
If it be boiled, this coloring matter separates, leaving the liquid clear 
and of a pale yellowish color. This liquid has the aromatic taste, 
and all the properties of soup made by boiling the flesh. "When 
evaporated and dried, a soft brown mass amounting to 12 or 15 per 
cent, of the weight of the original dnj flesh is obtained, having an 
intense flavor of roast meat. This extract of flesh is soluble in cold 
water, and when dissolved in about 32 parts of hot water, with salt, 
it gives to this water the taste and all the properties of an excellent 
soup. The hquid extract retains the peculiar taste of the flesh from 
which it was derived; so that if we add the concentrated juice of 
venison or fowl to exhausted beef, the latter at once acquires a venison 
or fowl taste. 

536. Loss of Weight in Cooking. — The first effect of applying a 
strong heat to a piece of fresh meat, is to cause the fibres to contract, 
to squeeze out a portion of the juice, and partially to close the pores so 
as to prevent the escape of more. Heat is applied to meats chiefly in 
three ways, ioiling, roasting^ and baling. During these operations, 
fresh beef and mutton, Avhen moderately fat, lose on an average 
about as follows: 





lu boiling. 


In baking. 


In roasting. 


4 lbs. of beef lose 


lib. 


1 lb. 3 OZS. 


1 lb. 5 02a. 


4 lbs. of mutton lose 


14 ozs. 


1 lb. 4 ozs. 


1 lb. 6 ozs. 



The greater loss in baking and roasting, arises chiefly from the greater 
quantity of water evaporated, and of fat which is melted out during 
these two methods of cooking. 

537. Best method of cooking Meat. — In preparing meat for the table, 



HOW COOKING CHANGES MEAT. 283 

we shall discover it to be most desirable that the iugredients 
of its juice should remain iu it; and this will depend much upon 
the method of culinary procedure. If the piece of meat be in- 
troduced into the water when Irislcly 'boiling^ the albumen at its 
surface, and to a certain depth inward, is immediately coagulated; 
thus enclosing the mass in a crust or shell which neither permits it3 
juice to flow out, nor the external water to penetrate within, to dis- 
solve, dilute, and weaken it. The greater part of the sapid consti- 
tuents of the meat are thus retained, rendering it juicy and well- 
flavored. It should be boiled for only a few minutes, and then kept 
for some time at a temperature from 158° to 165°. Meat is under- 
done or bloody, when it has been heated throughout only to the 
temperature of coagulating albumen (140°) ; it is quite done or cooked, 
when it has been heated through its whole mass to 158° or 165°, at 
which temperature the coloring matter of the blood coagulates. As 
in boiling, so in baking or roasting ; for whether the meat be sur- 
rounded by water, or in an oven, as soon as the water-proof coating 
is formed around it, the farther changes are effected alike in both 
cases, by internal vapor or steam. In roasting or baking, therefore, the 
fire should be at first made quite hot, until the surface pores are com- 
pletely plugged, and the albuminous crust formed. Hence, a beef- 
steak, or mutton-chop, is done quickly over a smart fire that the richly- 
flavored natural juices may be retained. 

539. Objection to the common method. — The fibrin of meat, in its 
natural state, is surrounded by an albuminous liquid. In coagulating, 
it becomes firm and hard, but at the same time, brittle and tender. 
If the albumen be coagulated within the meat, it forms a protective 
sheath around the fibres, and thus prevents them from being shrivelled, 
toughened, and hardened by boiling. This explains why the flesh of 
young animals, which is richer in albumen than that of old ones, is 
also more tender. If the meat be placed in cold water, and the 
temperature slowly raised to boiling, a portion of the savory and 
nutritive juices is dissolved out, and the meat becomes proportion- 
ally poorer for the loss. At the same time the fibres lose more or 
less of their shortness, or tenderness, and become tough. The smaller 
or thinner the piece of flesh is, the greater is its loss of savory con- 
stituents. If, in baking, the meat be exposed to a slow fire, its pores 
remain open, there is a constant escape of juice from within, and the 
flesh becomes dry and unsavory.* 

* The flesh of old animals often yields no more than 1 or 2 per cent, of albumen, that 
of young animals as much as 14 per coat. — Liebio. 



284 CULINARY CHANGES OF ALIMENTAET SITBSTANCES. 

540. Sonp, Beef-tea, Mntton-broth, 4c. — In the preparation of these 
our object is the reverse of that which has just been considered. We 
desire to take the nutritive and savory principles out of the meat, and 
get them into a liquid or soluble form. To obtain a liquid extract of 
meat, in the form of soup, broth, or tea, the flesh is finely chopped 
and placed in cold water, which is then slowly heated and kept boiling 
for a few minutes, when it is strained and pressed. In this manner 
we obtain the very strongest and best flavored soup which can bo 
made from flesh. " When one pound of lean beef, free of fat, and sepa- 
rated from the bones, in the finely -divided state in which it is used for 
beef-sausages or mince-meat, is uniformly mixed with its own weight 
of cold water, slowly heated to boiling, and the liquid after boiling 
briskly for a minute or two is strained through a towel from the coag- 
ulated albumen and fibrin, now become hard and horny, we obtain an 
equal weight of the most aromatic soup of such strength as cannot be 
obtained, even by boiling for hours, from a piece of flesh." — (Liebig.) 
To make the best article, it is desirable not to boil it long, as the ef- 
fect is to coagulate and render insoluble that which was extracted by 
cold water, and which should have remained dissolved in the soup. It 
is obvious from what has been said, that a piece of meat introduced 
undivided into boiling water, is in the most unfavorable condition pos- 
sible for making good soup. It is customary in soup-making to pro- 
tract the boiling for the purpose of thickening and apparently enrich- 
ing the soup. This is efiected by the gelatin, which is gradually 
extracted from the tissues, bones, and other parts, but in a nutritive 
point of view this ingredient is a fiction, as will be shown in the proper 
place (717). Soup-making is a kind of analysis of alimentary sub- 
stances used in its preparation — a part is taken, and a residue usually 
i-ejected. Yet it is clear that we shall have the completest nourish- 
ment by taking both parts, as the fibre of meat and the softened beans 
and peas of their respective soups. 

541. A new Broth for Strengthening the Sick. — In certain maladies (as 
typhus fever, for example, at particular stages), the greatest difliculty 
met with by the physician, lies in incomplete digestion, or inability 
promptly to reinforce the exhausted and bankrupt blood. To meet 
this difficulty Liebig prepared, as follows, a nutritive liquid, which 
has been used at Munich with the best results. Take half a lb. oi per- 
fectly fresh meat (beef or chicken), cut it in small pieces, add to it 1^ 
lb. of distilled (pure soft) water, with four drops of muriatic acid, and 
half a drachm of common salt ; mix the Avhole well together, and after 
standing an hour, strain through a common hair sieve, letting it pass 



PKEPAKATION AI^D PROPERTIES OF BUTTER, 285 

without pressing oi- squeezing. The portion passing through first be- 
ing cloudy, it is again poured through the sieve, and this process is 
repeated until it becomes perfectly clear. Upon the residue of meat 
remaining in the sieve, half a pound of distilled water is poured in 
small portions. In this manner a pound of cold extract of meat is ob- 
tained, of a red color, and pleasant meat-broth taste. It must not be 
heated, and is administered cold, by the cupful, according to the pa- 
tient's inclination. It is difficult to make it in summer, on account of 
its Mability to ferment and change. Perfectly cold water must be 
used, and refrigeration with ice will guard against decomposition. 

9. PREPAEATIOJr AND PROPERTIES OF BuTTER. 

542. Action of Heat upon Milk and Cream. — The gradual heating of 
milk facilitates the rising of its cream. The oil globules are broken, 
liquefied, run together, and ascend to the upper part of the vessel. 
There is always a trace of albumen in milk ; Avhen boiled this is coag- 
ulated and rises to the surface with oil globules, and forms there a 
pelicle or skin, which is increased by evaporation. The layer thus 
formed prevents the escape of steam, causing the liquid to boil over 
if the vessel is not removed from the fire. If cream be heated for 
some time nearly to boiling, its fat-globules melt together and collect 
upon the surface, as a fluid oil. When this is cooled it forms a very 
pure butter, which wUl keep long without being salted or becoming 
rancid, but has neither the fine flavor nor the firm consistence of 
churned butter. 

543. Batter separated meclianically. — If either milk or cream be beat- 
en or agitated mechanically for a time, the oil globules coalesce and 
form a mass of butter. It is believed that each little fat-globe is en- 
closed in a thin film of casein, which is ruptured by agitation. How- 
ever this may be, the oil-cells have sufficient resistance to require 
considerable mechanical violence to break them up, which is effected 
by churning. During this operation oxygen is absorbed from the air, 
the temperature rises, the cream or milk, if not already acid, turns 
sour, and gases are set free, which escape from under the cover, or 
when the churn is opened. 

544. Rate of Motion in Chnrning. — In churning cream, which is usu 
ally tliick and uneven, the agitation should at first be slow, until it has 
become completely broken into a uniform mass. As it becomes tliin- 
ner the motion is easier and may be slightly increased, and continued 
until a change in the sound from a low and smoorth to a harsh tone is 



286 CULINARY CUANGES OF ALIMENTABY SUBSTANCES. 

observed. It may tlieii be again slightly increased, until the butter 
Degins to form, when it is collected or 'gathered' by a slower move- 
ment. If the rate of motion in churning is too rapid, the cream is 
liable, especially at high temperatures, or in hot weather, to bunt, as 
it is called, while the butter is soft, frothy and bad. 

545. Time and Temperature. — With different churns, and at dif- 
ferent rates of speed, butter may be produced in from 10 minutes to 3 
or even 5 hours. Dr. Muspeatt assigns from 45 minutes to an hour as 
tlie best time for cream, while Prof. Attox states for cream an hour 
and a half, and for whole milk from two to three hours. Dickenson 
says it is no matter if we are six hours in churning sweet milk. It 
is, however, the well established result of experiment, Uiat the more 
quickly milk or cream is churned, the paler, softer, and poorer is the 
butter. It is said also that in over-churning, that is, when the opera- 
tion is too long continued after the butter is produced, it is apt to 
be softened and lightened in color, although the quantity may be 
somewhat increased. "We have had frequent occasion to notice the 
controlling influence of temperature over the changes of matter, and 
■we find it again illustrated here. Cream, when put into the churn, 
should never be warmer than 53° to 55°. It rises during churning 
from 4° to 10°. Johnston states that when the whole milk is churned, 
it should be raised to 65°. The careful regulation of the temperature 
is of the first importance, so that a thermometer is indispensable to 
the proper management of the operation. Some chai-ns have them 
attached, which is an excellent plan. The temperature of the cream 
Ls increased or diminished by mixing with hot or cold water, but many 
strenuously object to this. In some churns there is an outer chamber 
or vessel, which is separated from the cream by a thin sheet of metal, 
through which heat or cold readily passes from water contained in the 
chamber. This is a good arrangement, although the metal commonly 
used (zinc) is not quite free from objection (611). 

546. Composition and properties of Bntter. — The mass of butter is a 
tasteless and inodorous fat ; its pleasant aromatic flavor being due to 
a compound existing in it in very small quantity, namely, butyric acid, 
combined with oxide of lipyle. First quality butter has a pleasant 
peculiar aroma, is of a fine orange-yellow color, solid, and of a waxy 
or grained texture, exposing a different surfiice when cut from fat or 
grease. This granular quality results from the peculiar mode of its 
production, which is by the mechanical coherence of minute butter- 
particles or grains. "Were butter separated like lard, by melting, it 
would not present this appearance. Between good ordinary butter 



PKEP^ RATION AND PEOPEETIES OF CHEESE. 287 

and a first-rate article there is a wide difference ; the former is com- 
mon, the latter is but rarely seen. Cream and butter are both highly 
absorbent of unpleasant odors, and are extremely susceptible of taint 
from this cause. The air of the dairy-house must be "sweet as that 
wafted from the rose itself. A common farm cellar with meat, fish, 
and vegetables, would spoil the best package of butter ever made in 
sixty days." The cows should be kept on rich, tender, high-flavored 
grasses, — timothy, white clover, blue grass, red-top, with which the 
ground is to be thickly swarded over to protect it from sun and 
drouth. May, June and September are the best months, July and 
August being too hot ; while after frost appears, tlie grass becomes 
insipid and bitter, and will not yield butter of the best quality. 
Almost every kind of butter, however, i-s good when newly made. 
The vital considerations of its manufacture are connected with its 
quality of keeping, which will be noticed when we reach the subject 
of preservation (599). 

10. Preparation and Properties of Cheese. 

547. Spontaaeons Cnrdling of Jlilk. — When milk is left to itself for a 
time, which is shorter in warm or stormy weather, it sours and 
curdles, that is, its casein changes from the dissolved to the solid state. 
This is brought about by a series of interesting and beautiful changes 
originating in the unceasing activity of atmospheric oxygen. Casein, 
in itself, is insoluble in water. But it is of an acid nature, and is ca- 
pable of combining with potash or soda, and forming a compound 
which dissolves in water. Soda is the alkali which holds the casein 
of milk in solution. Now when fresh milk is exposed to the air, its 
oxygen acting upon a portion of the nitrogenous casein, changes it to 
a ferment ; and this takes effect upon the milk sugar, converting it 
into lactic acid, which causes the sourness of milk. When sufiicient 
of the lactic acid is thus formed, it seizes upon the soda, takes it away 
from the caseiu, and forms lactate of soda. The casein thus set free 
shrinks in bulk, and gathers into an insoluble, curdy mass, the opera- 
tion being aided by a gentle warmth. 

548. Artificial Cnrdling witli Acids. — In making cheese the milk is 
curdled artificially, and in different countries various substances are 
used for this purpose. But they all produce the effect in precisely the 
same way, that is, an acid substance is employed to neutralize the 
soda of the milk, by which the casein assumes the coagulated state. 
Almost any acid will have the effect of curdling milk. Muriatic acid, 
weakened with water, vinegar, tartaric acid, cream of tartar, lemon 
juice, and sour milk, are each used for the purpose. 



288 CULINARY CHANGES OF AJJMENTAEY SUBSTANCES. 

549. Artificial Curdling with Rennet. — The salted and dried stomach 
of the unweaned calf, lamb, or pig, is called rennet. If a small piece 
of this be soaked in water for a time, and the infusion be mixed -with 
milk at a temperature of 90° or 95°, curdling shortly takes place. It 
was once supposed that it is the acid of the gastric juice of the stomach 
which produces the change; but this cannot be, as the membrane acts 
with equal promptitude, though it has been thoroughly washed free 
from every thing of an acid nature. The change is due to the action 
of the animal matter itself. It is said that the rennet should never be 
used unless ten or twelve months old. During this period, by exposure 
to the air, a portion of the membrane has undergone decay and become 
soluble in water. This decomposing animal matter acts upon the 
sugar of milk, changing it to lactic acid, which produces curdling ex- 
actly as in spontaneous coagulation (547). There is much about the 
action of rennet that is not yet explained. Its condition seems to 
exert a decided influence on the quality of the cheese. The result is 
probably much influenced by the state of decay of the animal matter, 
as the decomposition may be so far advanced as to induce putrefaction* 
in the milk. 

550. Conditions of the preparation of Cheese. — By the action of curd- 
ling agents the milk is divided into two parts ; first the curd, com- 
prising all the casein, a large portion of oil and a trace of sugar of 
milk, with some water; and second, the whey or fluid part containing 
the bulk of water, the sugar of milk, and a small but variable propor- 
tion of oily matter. Of the saline matter in milk, the phosphates of 
lime and magnesia exist in the curd, while the remaining salts are 
found in the whey. The curd, separated from the whey and prepared 
in various ways, and then pressed, forms cheese. The properties of 
cheese are influenced by a great number of circumstances. Pure 
casein makes a cheese poor, hard, and liorny. The admixture of the 
oil or cream of the milk enriches it in proportion to its quantity. The 
most infei-ior cheeses therefore are made from milk that has been re- 
peatedly skimmed and deprived of all its oil, while the richest cheeses 
are those made directly from cream (cream cheeses), and which hence 
contain an excess of oily matter. Between these extremities there 
are all grades of quality, which depend upon the jiro'portion of the 
constituents. Thus if we use the new milk of the morning, mixed 
with the previous evening's milk that lias been deprived of its cream, 
we get a cheese of a certain quality ; if we use the xcholc milk of the 
previous night, the cheese will of course be better ; and if we use only 
the cream of the previous evening's milk, the cheese will be stUl 



PEOPERTIES AND PlIEl'AKATlON OF TEA. 289 

riclier. All the conditions which influence the properties of the mUk 
itself (334) affect also the quality of the cheese. The heat, in curd- 
ling, should not he too high, as it is apt to give excessive oiliness to 
the fatty portion of the milk. A thermometer affords more reliable 
indications than the sense of feeling. As soon as coagulation is com- 
plete, the curd should be separated, as the longer it stands the harder 
and tougher it is. Much judgment is required to know the proper 
quantity of rennet to be used ; if there is too little, the process is too 
slow, and time is given for the butter to separate itself from the curd, 
while too much rennet makes the curd tough, and otherwise affects 
disagreeably the subsequent changes and flavor of the cheese. The 
mode of separating the curd from the whey, its subsequent prepara- 
tion, and the degree and duration of the pressure applied, together 
with a great variety of other circumstances known to the skilful 
cheese-maker, have a powerful influence upon the quality of the arti- 
cle produced. "We shall refer to cheese again when speaking of preser- 
vation (C04). 

rV.— COMMON BEVERAGES. 
1. Peopeeties and Peepakation of Tea. 

551. The Tea Shrnb. — Tea consists of the prepared leaves of the 
tea-plant, a hardy shrub which grows from 3 to 6 feet high, chiefly in 
China. The plant is propagated from the seed, and matures in from 
two to three years, yielding usually three crops of leaves each season. 
When a year old, the young bushes are planted out in rows 3 or 4 
feet apart, and being cropped down so as to grow thick and bushy, the 
tea-field resembles a garden of gooseberry bushes. The leaves are 
picked by hand in May and June, and the plant yields leaves from 
four to six seasons. 

552. What causes different varieties of Tea. — Many varieties of tea of 
all grades of quality are known in market. These differences depend 
■first upon the soil, climate, culture, &c., of the locality where it is 
grown. Second, upon the time of picking ; the young unexpanded 
leaves that are gathered first being tender and delicate, while the sec- 
ond and third gatherings are more bitter, tough, and woody. Third^ 
the mode of treatment or preparation, which consists in drying, roast- 
ing, and rolling in the hand, by which the leaves acquire their twisted 
appearance, and finally sifting and winnowing. The methods of hand- 
ling arc various, and much depends upon them. 

553. Difference between Green and Black Teas.— All the different 
varieties of tea are classed as either rjreen or hlaclc. What constitutes 

13 



290 COMMON BEVERAGES. 

the real difference between these two «orts has long been a matter of 
doubt. It was at first supposed that they came from totally different 
species of plants ; but the latest accounts agree that they are both de- 
rived from the same plant, the difference being in conditions of growth 
and modes of dealing with the leaves. They may be thus contrasted : 

GEEEN TEA. BLACK TEA. 

1. Cultivated in manured soils. 1. Grown cluefly on the slopes of hills 

2. Leaves are steamed, withered and and ledges of mountains. 

roasted almost immediately after gather- 2. Allowed to be spread out in the air 

Ing. for some time after they are gathered. 

8. They are dried quickly after the 3. They are tossed about until they be- 

rolling process ; the whole operation being come soft and flaccid, 
brief and simple. 4. They are now roasted for a few min- 

utes, and rolled. 

5. They are exposed to the air for a few 
hours in a soft moist state. 

6. Lastly, they are dried slowly over 
charcoal fires. 

It is by lengthened exposure to the air in the process of diying, ac- 
companied perhaps by a slight heating and fermentation that the dark 
color and distinguishing flavor are given to the black teas of com- 
merce. The oxygen of the atmosphere acts rapidly upon the juice of 
the leaf during this exposure, and changes chemically the peculiar 
substances they contain, so as to impart to the entire leaf the dark 
hue it finally acquires. The precise nature of these changes has not 
been chemically investigated. — (JonxsTON.) The unchanging green 
color of green teas is produced, says Knapp, by employing steam to 
wither the fresh leaves, it being well known to collectors of plants, 
that many which inevitably turn black when simply dried, preserve 
their green color brilliant and permanent, when they are killed by 
steam, previously to drying. The same authority remarks, that green 
tea gives up much less of its juice in the drying process ; a circum- 
stance which fully explains its more energetic action upon the nervous 
system. 

554. Varieties of Green and Black Tea. — The most important teas of 
commerce may be thus arranged, beginning with the lowest qualities. 
Annexed is an approximative scale of the prices per pound paid for 
them in Canton. 

Green Teai. BUck Tea*. 

Twangay 18 to 27 cts. Bohca 12 to 18 cts. 

Hyson Skin 18 to 80 " Congou 22 to 25 " 

Young Hyson 27 to 40 " Campoi 22 to 80 " 

Hyson 40 to 56 " Souchong 20 to 35 " 

Imperial 45 to 58 " Caper 20 to 40 " 

Gunpowder 45 to 60 " Pekoe 35 to 75 " 



PBOPJEETIES AND PEEPAKATION OF TEA. 291 

Twang ay is the coarsest and most inferior of the green teaa. The 
Hysons are of a better quality, and are more widely used. The word 
' Hyson ' is derived from Hee-chun, the name of a celebrated Chinese 
tea-maker. Hyson-shin is composed of the light, inferior leaves, sepa- 
rated from Hyson by winnowing. Young-Hyson, Hyson, and Impe- 
rial, consist of the second and third crops; whUe Ounpowder, the 
finest of the green teas, consists of the first leaves, or leaf-buds, of 
the vernal crop. It is called 'gunpowder,' from the fancied resem- 
blance of its small rounded leaves to gunpowder grains. BoTiea is the 
poorest and cheapest of the black teas, and takes its name from being 
largely produced on the Bohea mountains ; Congou, fi-om cong-fou, 
' made with care,' and Souchong, from se-ou-chong, " a very little 
sort," are better varieties. Gape/r comes in little balls or grains, made 
up in the form of capers. Pekoe is the best of all the black teas, and 
corresponds to gunpowder among green teas. The word ' Pekoe,' or 
Pak-Ho, means ' white down,' and is applied to the first downy leaves 
of the spring growth. It is often called the Flowery Pehoe, which is 
erroneously supposed to refer to the blossom of the tea-plant ; but the 
tea flower itself has little fragrance, and although sometimes used in 
China, is not imported. 

555. Composition of Tea. — The analysis of tea shows it to be com- 
posed of four principal constituents. First, an aromatic, volatile oil, 
which produces the peculiar odor and flavor. It is of a citron yellow 
color, floats on water, and when exposed to the air is quickly convert- 
ed into a solid resin by atmospheric oxygen. It has such a powerful 
taste, that when placed on the tougue it spreads over the entire throat, 
and exerts a painful action upon the nerves. It does not exist in the 
fresh or natural leaves, but is produced during the roasting process. 
A hundred pounds of tea yield only a single pound of the oil. Second, 
tea contains a peculiar principle called thein, a substance rich in nitro- 
gen, and classed among vegetable alkalies. Stenhouse states that or- 
dinary tea contains about two per cent, of thein ; but Peligot has 
found as much as 6 per cent, in certain green teas, although this quan- 
tity is very unusual. Thein has a slightly bitter taste, no smell, and 
dissolves in hot water. An infusion of tea, therefore, contains dis- 
solved thein : and if the leaves be of good quality, an ounce will yield 
about 10 grains. Third, tannin or tannic acid, a substance so named 
because it is the ingi-edient in oak and hemlock bark, which combines 
with leather in the operation of tanning. If a compound of iron (sul- 
phate of iron — copperas, for example), be introduced into an infusion of 
tea, it turns it to an inky blackness, by precipitating its tannic acid. 



292 COMMON BEVKRAGES. 

This substance is a powerful astringent, and gis^es to tea its astriugent 
taste and properties. It forms from 12 to 18 per cent, of the weight 
of tea. When tea is steeped, the three foregoing constituents are com- 
municated to the water; they hence give its active properties to the 
ordinary beverage. But tea leaves contain, fourthly^ another constit- 
uent, namely, gluten — which^not being dissolved by hot water, is 
usually lost with the dregs or grounds. The proportion of this sub- 
stance is stated to be as high as 25 per cent., so that the leaves, after 
exhaustion by steeping, are still highly nutritive. In some localities 
it is customary to eat them. 

556. How Tea is best made. — The Chinese method is to throw some 
tea into a cup, and pour boiling water over it ; they cover the cup 
with a shallow saucer, and let it rest for some time. After it has 
stood sufficiently long, they pour the clear liquid Into a saucer, and 
drink it hot. Various methods are pursued in different countries, but 
a knowledge of the composition and properties of tea is the best guide 
in preparing its infusion. It is desirable to obtain from the leaves the 
largest possible amount of matter which water wiU extract, and retain 
them in the liquid. The thein of tea is in combination with tannic acid, 
forming a compound which requires boiling water to dissolve it. But, 
on the other hand, the aromatic oil of tea is volatile, so that the boil- 
ing tends to drive it off with the steam into the air. If lukewarm 
water is used, the most important element of tea, its thein, is not ob- 
tained ; while, by boUing, its fragrant aroma is wasted. The plan to 
be pursued, therefore, is to pour boiling water upon the tea, in close 
vessels^ so that its active ingredients may be dissolved, and at the same 
time the volatile oil retained in the mixture. In cooling, a good de- 
coction of tea becomes slightly turbid, the tannate of tJiein being no 
longer held in solution, is precipitated and rises, forming a skin upon 
the surface. 

557. What remains in tlie Grounds, or residue. — If tea be steeped in 
water below the boiling temperature, an infusion is obtained, having 
the peculiar tea-taste, but the thein is not obtained ; a second infusion 
of the leaves with boiling will extract the thein, and tannic acid, 
60 that, although it may be less fragrant, it wUl be more active. The 
leaves which have been used of course vary in composition, according 
to the completeness of the first exhaustion. By the common method 
of extraction, the entire quantity of tliein is never dissolved, about 
one-third being left in the leaves. Mulder foimd hot Avater to ex- 
tract from six specimens of black tea, from 28 to 38 per cent, of their 
weight ; of the same number of kinds of green tea, fi-om 34 to 46 per 



PBOPEBT/iiS AND PKEPARATION OF COFFEE. 293 

cent. Peligot procured from black tea an average of 38 per cent., 
and from green, 43 per cent. Yet the quantities are by no means con- 
stant, as different samples of the same color and name in the market 
yield very different proportions of soluble matter. Teas prepared from 
young leaves furnish more soluble matter than the older leaves ; while 
green teas give more of light-colored, and black of dark-colored ingre- 
dients. The gluten, in which tea leaves are rich, is not dissolved by 
boiling water ; but water made slightly alkaline dissolves gluten. It 
has therefore been recommended that a little soda be added to the 
water, which would have the effect of making the tea slightly more 
nutritious. 

558. Adnlterations of Tea. — Teas of all sorts are liable to the grossest 
adulterations. The green teas are extensively stained or painted by 
the Chinese, to heighten their green color. For this purpose they use 
Prussian blue, indigo, turmeric, gypsum, and China-clay. With these 
ingredients they glaze or face the surface of the leaves, to such an ex- 
tent, that it is affirmed we never get pure green tea. Other leaves are 
also often mixed with those of the tea-plant, by the Chinese. In Eng- 
land, the leaves of the sloe and thorn are much mixed with tea. The 
Chinese also make a crude and worthless preparation of sweepings, 
dust, sand, leaves, and various impurities of the tea warehouses, cement- 
ed with gum or rice-water, which they honestly call lie-tea^ and employ 
it extensively to mix with other teas. In England, exhausted leaves 
are bought up, their astringent property restored by the addition of 
catacTiu (a concentrated tanning extract), and colored with black lead, 
logwood, «&c., are sold again as genuine tea. Another fraud of great 
prevalence consists in mixing inferior qualities of tea with the better 
sorts, and cheating the purchaser by selling the compound at the price 
of the best article. To detect indigo or Prussian blue in tea, let a por- 
tion of it be shaken with cold water and thrown upon a bit of thin 
muslin, the fine coloring matter will pass through the muslin, and 
settle to the bottom of the water. When the water is poured off, the 
blue matter may be treated with a solution of chloride of lime. If it 
is bleached, the coloring matter is indigo. If potash makes it brown, 
and afterwards a few drops of sulphuric acid make it blue again, it is 
Prussian blue. — (Johnston.) 

2. Properties and Preparation of Coffee. 

559. The Coffee Tree and its Seeds.— Coffee is the product of a plant, 
grown extensively in warm climates. The natural height of the tree, 



294 COMMOX BEVERAGES. 

varies from 10 to 30 feet ; but it is usually pruned down to 5 or 6 feet, 
to increase the crop of fruit. All are familiar ■with the structure 
of coflfee seeds ; they are of an oblong figure, convex on one side, 
and flat, with a little straight furrow, on the other. They are en- 
closed in a pulpy berry of a red color, which resembles a cherry, and 
are situated within it with their flat sides together, and invested by a 
tough membrane called the parchment. The seeds are separated by 
fermenting the berries, crushing them under heavy rollers, drying, 
grinding, and winnowing. 

5G0. Varieties of Coflfee. — The best coffee is the Arabian; that 
grown in the province of Mocha {Mocha coffee) is of the finest quality. 
It may be known by having a smaller and rounder berry than any 
other, and likewise, a more agreeable smell and taste. It is of a dark 
yellow color. The Java and East Indian coffees are larger and of a 
paler yellow, while Ceylon, West Indian, and Brazilian coffees are of 
a bluish or greenish gray tint. 

561. Composition of CoffcCi — The raw coffee, as it comes to market, 
Is but slightly aromatic ; its odor is faint, while its taste is moderately 
bitter and astringent. In this state its composition, according to 
Paten, is as follows : 

Water 12 

Gum and Sugar 15'50 

Gluten 13 

Cafein 00-75 

Fat and Volatile Oil 13 

Tannic Acid 5 

Woody Fibre 84 

ABh 6-75 

Dr. Stentiottse states that it contains 8 per cent, of cane sugar. Cof 
fee, it will be seen, contains tannin, the same astringent principle as 
tea, but in much smaller proportion ; and the substance itself is of 
a somewhat different chemical nature. They both contain much 
gluten ; but the most remarkable point of similarity between tea and 
coffee, is found in the fact, that the cafein of coffee is a vegetable 
alkali, with the same composition and properties as thein of tea. A 
direct analysis of the two substances gave the following result : 

Carbon. Nitrogen. Hydrogen^ Oxygen. 

Thein 50-1 29-0 6-2 15-7 

Cafein 49-3 28-8 5-1 16-2 

The proportion of cafein in coffee is probably somewhat higher 
than the preceding analysis indicates. It is of course variable ; but 
is about half that of thein in tea (555). Coffee, however, is not used 



PEOPERTIES AND PKEPAEATIOX OF COFFEE. 



295 



Fig. 104. 







in the raw or natural state ; like tea, it is first altered by heat or 
roasted. 

562. Effects of roasting Coffee.— 

The operation of roasting, produces 
several important changes in coffee. 
In the first place, the raw coffee- 
berries are so tough and horny, 
that it is very difiicult to grind, and 
pulverize them sufliciently fine, that 
water may exert its fuU solvent 
effect upon them. Boasting ren- 
ders them yielding and brittle, ^ 
so that they may be more readily 
ground ; while, at the same time, it 
increases the amount of matter so- 
luble in hot water. If we examine 
the raw coffee seed with the micro- 
scope, it will be found to consist of 
an assemblage of cells, in the cavi- 
ties of which are seen small drops 
of the aromatic volatile oU of cof- 
fee. This appearance is shown in 
(Fig. 104). If now we place a 
fragment or section of roasted cof- 
fee under a magnifier, it will be 
observed that these drops of oQ 
in the cells are no longer visible 
(Fig. 105). They have, in part, 
been dissipated by the heat, and 
in part, become more generally dif- 
fused throughout the mass of the 
seed; a portion being driven to the 
surface. It is obvious, that roasting 
produces certain chemical changes 
in coffee, which alter its flavor and 
taste, and bring out the peculiar 



Appearance of unroasted coffee-berries 
magnified, showing the size and form of 
tlie cells, and the di-ops of oil contained in 
their cavities. 



Fro. 105. 







and highly esteemed aroma for -i^-/^ 
which this beverage is distinguish- ■^PP«»^'''>«« °f ^ o^^t^d ''^^'^ """'^^ 
ed. Johnston states that the peculiar aromatic principle which gives 
flavor to coffee, exists in extremely minute quantity, (one part in fifty 
thousand,) and is generated in the roasting process. The heat also 



296 COMMON BEVEEAGES. 

sets a portion of the cafein free from its combination with tannic 
acid, and evaporates it. The temperature is sufficiently high to de- 
compose the sugar, and change it to brown, burnt sugar, or caramel. 
Coffee darkens in color during roasting, swells much in bulk, and 
loses a considerable portion of its weight, by evaporation of its water 
and loss of other constituents. Coffee roasted to a reddish brown, 
loses in weight, 15 per cent., and gains in bulk, 30 per cent. To a 
chestnut irown, it loses 20 per cent, in weight, and gains 50 in 
bulk. To a dai'h iroicn, it loses 25 per cent, of weight, and gains 
50 in bulk. 

5G3. Hiflts concerning the Roasting Process. — The roasting of coffee 
is an operation of considerable nicety; more, perhaps, depending 
upon it than upon the variety of the article itself. Coffee is roasted 
by the dealers, in hollow iron cylinders or globes, which are kept 
I'evolving over a fire. As the first effect is the evapoi*ation of a consid- 
erable amount of water, if the vessel be close this is retained, and the 
coffee roasted in an atmosphere of its own steam. This is not thought 
to be the best plan, and if the operation be carried on at home, it is 
recommended that the coffee be first dried in an open pan over a 
gentle fire, untU it becomes yellow. It should then be scorched in 
a covered vessel, to prevent the escape of the aroma ; taking care, 
by prefer agitation, to prevent any portion from being burnt ; as a 
few charred grains communicate a bad odor to the rest. It is impor- 
tant that just the right temperature should be attained and kept. If 
the heat be too low, the aromatic flavor is not fully produced, and if 
it be too high, the rich oUy matter is dissipated, leaving only the 
bitterness and astringffacy of the charred seeds. The operation should 
be continued until the coffee acquires a deep cinnamon or chestnut 
color, and an oily appearance, and the peculiar fragrance of the roasted 
coffee is sufficiently strong. It may then be taken from the fire, 
and allowed to cool without exposure to the air, that the aromatic 
vapor may condense and be retained by the roasted grains. Coffee is 
very apt to be over-roasted, and even a slight excess of heat greatly 
injures its properties. 

5G4. Effects of Time upon Coffee. — Coffee berries undergo a change 
called ripening, by keeping ; that is, they improve in flavor. The 
Arabian coffee ripens in three years, and it is said that in ten or a 
dozen years the inferior American coffees become as good, and acquire 
as high a flavor as any brought from Turkey. — (Ellis.) But it is differ- 
ent after the coffee is roasted and ground. Its flavoring ingredients 
have a tendency to escape, and it should therefore be confined in ves- 



PBOPERTIES AND PKEPABATION OF COFFEE. 297 

eels closed from the air. It should not be exposed to foreign or dis- 
agreeable odors, as it has a power of imbibing bad exhalations, by 
which it is often injured. Many cargoes of coffee have been spoiled 
from having been shipped with, or even put into vessels which had 
previously been freighted with sugar. A few bags of pepper are suffi- 
cient to spoil a whole ship-load of coffee. — (Noemandt.) 

565. Mode of Preparing the Beverage. — To prepare the coffee, it 
should be roasted and ground just before using, no more being ground 
at a time than is wanted immediately. Of course the finer it is re- 
duced the stronger will be the extract from a given weight of coffee, 
one-fourth more soluble matter being obtained from coffee ground to 
the fineness of flour than from the ordinary coarse powder (Knapp). 
If a cup of good coffee be placed upon a table, boiling hot, it will fill 
the room with its fragrance. Its most valuable portion is thus liable 
to be exhaled and lost. Hence the same difficulty is encountei-ed as 
in tea making ; boiling dissipates the much -prized aroma ; but a high 
heat is necessary to extract the other important ingredients of the 
coffee. It should therefore be steeped rather than boiled, an infusion, 
and not a decoction being made. Some make it a rule not to suffer 
the coffee to boil, but only to bring it just to the boiling point. Yet, a 
few minutes' boiling undoubtedly increases the quantity of the dis- 
solved, bitter, exhilarating principle. Dr. Donovan recommends that 
the whole of the water to be used be divided into two parts, one half 
to be put on the fire with the coffee, and, as soon as the liquor boils, 
taken off", allowed to subside for a few seconds, and then pom-ed off as 
clear as it will run. Immediately the remaining half of the water, at 
a boiling heat, is to be poured on the grounds ; the coffee pot is to bo 
l)laced on the fire and kept boiling three minutes, and after a few mo- 
ments' settling, the clear part is to be poured off and mingled with the 
first. The mixture now contains a large share of the qualities of the 
coffee, both aromatic and bitter. 

506. Alkaline Water for Coffee-making. — It is observed, that some 
natural waters give a stronger and better flavored coffee than others, 
and this has been traced as in Prague, to the presence of alkaline mat- 
ter in those whicb give the most agreeable infusion. Hence, to obtain 
a more uniformly strong and well-flavored coffee, it is recommended 
to add a little soda to the water with which the infusion is made. 
About forty grains of dry, or twice as much of crystallized carbonate 
of soda, are sufficient for a pound of coffee. — (Johnston.) 

567. Adnlterations of Coffee. — Ground coffee is very extensively 
adulterated. Various substances are employed for this i)urpose, as 

13* 



298 COMMON BEVERAGES. 

roasted peas, beans, and corn, and dried and roasted roots, such as tur- 
nips, carrots, potatoes, &c. But the most common adulterant is cMccory, 
a plant of the dandelion tribe, which has a large, white parsnip-like 
root, abounding in a bitter juice. The root is mashed, sliced, dried, 
and roasted with about two per cent, of lard, until it is of a chocolate 
color. A little roasted chiccory gives as dark a color and as bitter a 
taste to water, as a great deal of coffee ; and, costing only about one- 
third ae much, the temptation is strong to crowd it into ground coffee. 
So common has the use of chiccory with coffee, become, that it has, 
in fact, created a taste for a solution of unmingled chiccory, as a bever- 
age, although it is destitute of any thing corresponding to the cafein, 
or exhilarating principle of coffee. As an illustration of the extent of 
adulteration, and how one fraud opens the door to another, it is found 
that pure chiccory is almost as difficult to be met with in market as 
unadulterated coffee. Venetian red is employed to impart to it a true 
coffee coloi*, while brick dust is used by the painter to cheapen and 
modify the shade of his Venetian red. 

568. How the Cheats in Coffee may be Detected. — When cold water is 
poured upon coffee the liquid acquires color only very slowly, and it 
does not become very deep after prolonged soaking; even when 
boiling water is employed, the infusion, although somewhat deeper, 
stUl remains clear and transparent. "When, however, cold water is 
poured upon roasted and ground chiccory root, it quickly becomes of 
a deep brown, and in a short time is quite opaque ; with boiling water 
the result is still more prompt and marked. We may therefore detect 
chiccory in a suspected sample of coffee by placing a little in cold 
water. If it be pm-e the water will remain uncolored ; if chiccory be 
present it will be strongly discolored. It may be remarked, however, 
that if the coffee should be adulterated with burnt sugar, it will pro- 
duce a similar coloration of the water. It may be further noticed that 
particles of coffee float upon water, and, owing to their oiliness, are 
not melted, while chiccory absorbs water and sinks. The admixture 
of burnt and ground beans, peas, and grain, is not so readily shown. 
The most certain method of detecting these is by microscopic exami- 
nation. 

3. Cocoa and Chocolate. 

569. Source aad Composition of Cacao Seeds. — These beverages are 
prepared from the cacao beans, which are derived from a fruit resem- 
bling a short, thick cucumber, grown upon the small cacao tree of the 
West Indies, Mexico, and Soutli America. The beans are enclosed io 



COCOA AND CHOCOLATE. 299 

rows, in a rose-colored, spongy substance, like that of the watermelon. 
When shelled out of this fleshy part, they are surrounded by a thin 
skin or husk, which forms about 11 per cent, of their weight. The 
cacao bean is brittle, of a dark brown color internally, cuts like a rich 
nut, and has a slightly astringent, but decidedly bitter taste. In pre- 
paring it for use, it is roasted, in the same way as coflfee, until the 
aroma is fully developed. The bean is now more brittle, lighter 
brown in color, and less astringent and bitter than before. The fol- 
lowing is its composition, according to Lampaditjs : 

Fatty matter, 53-16 

Albuminous brown matter, containing the aroma of the bean, 16-70 

Starch, 10-91 

Gum, 7-75 

Lignin, '90 

Eed coloring matter, 2-01 

Water, 5-20 

Loss, 8-43 

The largest constituent is a fatty substance, called Irctter of cacao^ of 
the consistence of tallow, white, of a mild, agreeable taste, and not 
apt to turn rancid by keeping. Cacao beans have also been found to 
contain a substance, in minute proportion, not included in this analysis, 
called theobromine a nitrogenous body, similar in nature and properties 
to thein, of tea, and (jafeine of coffee. 

570. Forms of Preparation. — It is prepared in three ways. First. 
The whole bean, after roasting, is beat into a paste in a hot mortar, or 
ground between hot rollers. This paste, mixed with starch, sugar, &c., 
forms common cocoa, sold under various names, as ' rich cocoa, ' 
' flake cocoa,' ' soluble cocoa,' &c. These are often greatly injured 
from the admixture of earthy and other matters, which adhere to the 
husk of the beans. Second. The bean is deprived of its husk, and then 
crushed into fragments. These form commercial cocoa niis, the purest 
state in whicli cocoa can be obtained from the retail dealer. Third. 
The bean, when shelled, is ground at once into a paste by means of 
hot rollers, mixed with sugar, and seasoned with vanilla, and some- 
times with cinnamon and cloves. This paste forms chocolate. — 
(Johnston.) 

571. How these preparations are used. — First, the chocolate is made 
up into sweet cakes, sugar confectionery, &c., and is eaten in the solid 
state as a nutritious article of diet, containing in a small compass much 
strengtli-sustaining capability. Second^ the chocolate or cocoa is 
scraped into powder and mixed with boiling water, and boiling milk, 
when it makes a beverage somewhat thick, but agreeable to the pal- 



300 PEESERVATIOlsr OF ALIMENTAEY SUBSTANCES. 

ate, refresliiBg to the spirits, and highly nutritious. Th ird, the nibs are 
boiled in water, with which they form a dark brown decoction, which, 
like coffee, is poured off the insoluble part of the bean. With sugar 
and milk this forms an agreeable drink, better adapted for persons of 
weak digestion than the entire bean. The husk is usually ground up 
with the ordinary cocoas, but it is always separated in the manufac- 
ture of the purer chocolates. 

572. Adalteration of Chocolate. — Pure or genuine chocolate should 
dissolve in the mouth without grittiness, and leave a peculiar sensation 
of fi'eshness, and after boiling it with water, the emulsion should not 
form a jelly when cold ; if it does, starch or flour is present. Many 
of the preparations of the cocoa-nut, sold under the name of chocolate 
powder, consist of a most disgusting mixture of bad or musty cocoa- 
nuts, with their shells, coarse sugar of the very lowest quality, ground 
with potato starch, old sea-biscuits, coarse branny flour, animal fats 
(generally tallow). I have known cocoa-powder made of potato 
starch moistened with a decoction of cocoa-nut shells and sweetened 
with molasses ; chocolate, made of the same materials, with the ad- 
dition of tallow and ochre, a coarse paint. I have also met with 
chocolate in which brick-dust, or red ochre, had been introduced to 
the extent of 12 per cent. — (Noemaxdy.) The temptation to fraud in 
these preparations seems to be as irresistible as in the case of ground 
cofiee. There is no easy means of detection short of refined micro- 
scopic and chemical examination, so that the only practicable means of 
self-defence for the purchaser, is to deal only with traders of unques- 
tionable integrity, where such can be found. 

v.— PRESERVATION OF ALIMENTARY SUBSTANCES. 
1. Causes of theie Changeableness. 

573. Why is it Necessary that Foods should be Perishable ? — As in the 

plan of nature the production of force depends upon change of matter, 
and as the fundamental purpose of animal life is the evolution of pow- 
er, it is apparent that matter which is to act as food, must be capable 
of ready and rapid transformation. This inherent fticility of change, 
by which alimentary substances are conformed to the deep require- 
ments of the animal economy, renders them extremely transient and 
perishable. If they are designed for change within the body, they 
must be subject to change without. In order tliat the gluten of flour, 
for example, may pass readily through the successive changes of the 
animal organism, being converted first into blood, then into musculat 



CAUSES OF THEIR CHANGEABLENESS. 301 

fibre, and then decomposed for the development of contractile force, it is 
necessary that this substance should be so loosely built up, the attrac- 
tions amongst its atoms should be so feeble, that slight causes become 
capable of breaking down its chemical structure. 

574. Change of Nntrient Matter within and without the Body. — It was 
formerly taught that the living body is the domain of a peculiar vi- 
tal power, which suspends the ordinary destructive play of chemical 
affinities and physical forces, but that at death the vital energy ceases, 
and those forces resume their natural activity, causing the speedy dis- 
organization of the inanimate organism. But this is hardly correct. 
The vital force, or whatever we may name the presiding agency of 
the living system, does not suspend physical and chemical laws, but 
only regulates, and as it were uses them. We have already seen that 
strictly chemical changes go on constantly in the body, and shall 
shortly have occasion to notice their extent (624). They are of the 
same kind {oxidations)^ are carried on by the same agent {atmospheric 
air\ and yield the same final products (carbonic acid, water and am- 
monia), in both conditions. In the living fabric the decompositions 
are measured ; while in the lifeless body they are uncontrolled, and 
quickly spread through the entire organic mass. 

575. Conditions of the Perishableness of Foods. — Alimentary substances 
are by no means alike changeable ; some keep longer than others un- 
der the same circumstances. There are certain specific causes of or- 
ganic decomposition, and accordingly as these act conjointly, or with 
variable intensity, is the rate of putrefactive change. In chemical 
composition, vegetable and animal substances are much more compli- 
cated than mineral compounds, and hence they are less permanent. 
Generally, mineral substances are combined in the simplest and 
most stable way, containing but few atoms, and consisting of pairs of 
elements, with nothing to disturb their direct attraction for each other. 
On the contrary, organized substances, in some cases, contain several 
hundred atoms, and consist of three, four or five difterent elements, 
joined by complex afiinities into delicate and fragile combinations. 
"We have seen, in speaking of fermentation, that albuminous substan- 
ces are, from this cause, moat changeable, and are universally present 
in substances designed for food. "Water is a large constituent of 
all alimentary bodies, in their natural state, and is highly promotive 
of chemical changes ; indeed, it is indispensable to them. Tem- 
perature exerts an all-controlling influence — warmth favoring, and 
cold retarding, or aiTcsting, these transformations. The atmospheric 
medium, which is in contact with every thing, contams an element 



302 PRESERVA-TION OF ALIMENTARY SUBSTANCES. 

which is the ever-active and eternal enemy of organization. The in- 
satiable hunger of oxygen gas for the elements of organic substances, 
is a universal cause of decomposition — it is the omnipresent destroyer, 
consuming alike the li ving and the dead (662). Putrefactive decay may 
also be prevented by certain chemical substances which are used for the 
purpose. A knowledge of the laws and conditions of organic decom- 
position, has led to various practical methods of controlling it, which 
constitute the art of preserving. 

2. Peeservation bt Exclusion of Am. 

576. Oxygen as an exciter of decay. — Other conditions being favor* 
able, that is, moisture being present and a proper temperature, access 
of air starts decomposition, — it is the prime mover of the destructive 
processes. "We have already noticed its mode of action, in speaking of 
fermentation (488). In the case of vegetables, as potatoes and apples, 
for example, if the air is excluded from their interior, they remain 
for a considerable time sound. But if we cut them, the oxygen 
quickly attacks the exposed surface and turns it brown, indicating the 
incipient stage of decay. "When the surface of fruits and vegetables 
is injured, so that their juices come in direct contact with the air, the 
eflfect is at once seen. If an apple is bruised, the injured spot imme- 
diately turns dark, and decomposition gradually spreads from that 
point, until the whole apple becomes rotten. The juice of the ripe 
grape, while protected from air by an unbroken skin, remains sweet 
and scarcely changes ; it may be dried and converted into a raisin, 
its sweetness remaining. If it be crushed under mercury, and the 
juice be collected in a glass completely filled with mercury, so as to 
prevent all contact of air, it will remain unchanged for several days. 
But if air be once admitted, as by perforating the grape-skin with a 
needle's point, fermentation commences almost instantaneously, and the 
juice is soon entirely changed. The same is true of all animal fluids. 
Milk, while in the udder of the healthy cow undergoes no change, 
but in contact with air, its properties are soon totally altered — it is 
soured and coagulated (547). "When life has been destroyed by bodily 
wounds, decomposition spreads from them ; or if the animal have not 
died by violence, the changes may begin internally in those parts, 
Buch as the lungs, which are in contact with the air. 

577. Changes begun by Oxygen may proceed without it. — It is by no 
means necessary, in all cases, that air should be in constant contact 
with the changing substance; the decomposition once commenced. 



BY EXCLUSION OF AUS. 303 

may continue, though the oxygen be entirely excluded. Milk, if once 
exposed to the air, coagulates and sours, though sealed up in air-tight 
vessels. Grape juice, tliough oxygen be completely cut off, ferments, 
generates gases, and often explodes the bottles in which it is confined. 
The impulse of disorganization being given, decomposition goes on 
without further external aid. To explain this, we must suppose that 
the atoms of the changing substance were at first in a kind of rest or 
equilibrium, without mutual activity, and that by the invasion of oxy- 
gen, this equilibrium has been disturbed, so that the elements of the 
substance begin to act and re-act upon each other, giving rise to new 
products. In this way, a state of change commenced by merely jost- 
ling a few surface atoms through contact of oxygen, is propagated by 
intestinal action throughout the entire mass. 

578. How changes begun by Oxygen may be stopped. — " Tlie property 
of organic substances to pass into a state of fermentation and decay 
in contact with atmospheric air, and in consequence to transmit these 
states of change to other organized substances, is annihilated in all 
cases without exception, hy heating to the toiling pointy — ^Liebig. 
The substance most prone to be affected by air-contact, is liquid albu- 
men ; and this by boiling is solidified, and so altered in properties, as 
to lose its peculiar susceptibility of transmutation. The boiling cer- 
tainly obliterates the effect that oxygen has produced, and as the 
atoms of matter have no inherent power to put themselves in motion, 
and cannot change place unless influenced by some external cause, it 
is obvious that the nutritive substance will remain unaltered if the 
air is Tcept excluded. These facts indicate the most certain, manage- 
able, and perfect method of preserving alimentary substances. By 
simply heating to the boiling point, which produces no other change 
than that of partial cooking, and afterward protecting from the air, 
alimentary substances, both animal and vegetable, may be preserved 
in their natural condition entirely unchanged in both flavor and pro- 
perties, for an indefinite period. This plan was first brought into 
general notice by M. Appeet of France, in 1809. He preserved all 
kinds of fruits, vegetables, meats, soups, &c., in glass bottles. His prac- 
tical methods, however, were crude and unsatisfactory, and have been 
superseded by others. Captain Koss presented the society of arts with 
a box from the house of Gamble and Daekhst (London), which con- 
tained cooked provisions sixteen years old, and that were in a state of 
perfect preservation. The details of the preparation on a large scale, 
as practised chiefly for marine consumption, we have no space liere 
to describe. The vegetables, meats, poultry, «Ssc., are cooked precisely 



304 PBESERVATION OF ALIMENTAEY SUBSTANCES. 

in the same manner as for immediate consumption, and tlien sealed 
up in boxes and canisters which do not contain a particle of air. 

579. Domestic preservation in air-tight vessels. — The preservation of 
delicate fruit and vegetables in air-tight cans, has now become quite 
generally a houseliold operation, and there can be no doubt that as 
people acquire experience in the process, they will employ it much 
more extensively. Of this process Prof. Likbig remarks, "The pre- 
pared aliments are enclosed in canisters of tinned iron plate (609), 
the covers are soldered air-tight, and the canisters exp\jsed to the 
temperature of boiling water, "When this degree of heat has pene- 
trated to the centre of the contents, which it requires about three or 
four hours to acomplish, the aliments have acquired a stability which 
one may almost say is eternal. When the canister is opened, after 
the lapse of several years, the contents appear just as if they were only 
recently enclosed. The color, taste, and smell of the meat, are com- 
pletely unaltered. This valuable method of preparing food, has been 
adopted by many persons in my neighborhood, and has enabled our 
housewives to adorn their tables with green vegetables in the midst 
of winter, and with dishes at all times which otherwise could be ob- 
tained only at particular seasons." 

580. Canisters closed by soldering. — Perfectly tight tin canisters of 
almost any convenient shape are provided, and the article to be pre- 
served, sometimes raw, but generally cooked, is placed within it, and 
the lid soldered down. The lid, is however, perforated with a small 
aperture or pin-hole. The canister is then placed in boiling water, and 
the moisture within is converted into steam which drives out the air. 
The boiling is continued as long as may be required totally or partially 
to cook the contents of the can, which is then withdrawn, and the 
pin-hole closed with solder. This is an operation of considerable 
nicety. The heat drives out not only air contained in the canister, 
but also a jet of steam. The solderer, therefore, lets fall a few drops 
of cold water on tlie tin around the aperture, producing a momentary 
condensation of the steam, during which the pin-hole is dexterously 
closed. The delicacy and success of the operation, consists in carry- 
ing the condensation only so far as just to arrest the jet of steam, and 
in closing the opening at the instant. After the canister is closed, 
it is again exposed with its contents for a short period to a boiling 
heat. 

581. Spratt's scIf-scatlng Cans. — In many cases a tinsmith may not 
be near, and the soldering operation for closing the canisters will be 
quite certain to fail in the hands of the inexperienced. To obviate 



BY EXCLUSION OF AIR. 



305 



this difficulty, other arrangements have been contrived. Speatt's 
cans* are oblong tin cylinders (Fig. 106), holding from a quart to a 
gaUon, which are closed with a screw acting upon a ring or ' com- 
press' of india-rubber, and then hermetically sealed witli beeswiis. 
The closure is simple and effectual, and can be managed with a little 
care by any body. The articles being introduced into the can, the cap 
is screwed down tightly with the fingers^ and the can" submerged in a 

boiler of cold water, which is then raised ^ 

' Fig. 106. 

to boiling. After boiling a sufficient time 

they are withdrawn, the caps unscrewed^ /-^^'^^iSlla^^li 

and the cans left open for one minute. If k, 

the previous boiling has been thorough, 

steam will escape freely. If it does not ' 

so escape, the boiling must be repeated. 

The cap is then screwed down, this time 

very tightly, xoith a icrench provided, and 

the can introduced into the water and 

boiled a second time. On withdrawing it 

again melted beeswax is poured into a 

little channel or groove, which makes the 

sealing perfect, if the cap fits and is tightly 

screwed down. In aU cases there are at 

least two boilings. The second might be ^P'""'' Seif-seaiing Can. 

thought unnecessary, but it is not. The vessel must be opened, that 

the steam may drive out the air, and there is always the possibility 

that a trace may be left. If so, during the second boiling the oxygen 

will be entirely converted into carbonic acid, which is innoxious. As 

the results of large experience the times required for the boiling are 

as follows : 

First boiling. Second boiling. 

Berries Of all kinds 15 minutes. 5 minutes. 

Cherries or currants 15 " 5 " 

Khubarb 15 « 5 « 

Peaches 20 " 5 " 

Plnms 20 " 10 

Quinces, pears or apples 45 « 15 " 

Tomatoes 30 " 15 " 

Asparagus 60 " 80 " 

Green peas, corn or beans 3 hours. 8 hours. 

582. Suggestions concerning tlie use of tlic Cans.— -None but perfectlj 
fresh sound fruit should be put up in the above manner. It is recom- 




♦ Manufactured by Wells & Provost, New York, 



806 PEESERVATION OF ALIMENTARY SUBSTANCES. 

mended that peaches, quinces, pears and apples be peeled, and the 
seeds removed before preserving, as seeds and peel embitter and other- 
wise injure the flavor. Peach stones contain traces of Prussic acid, a 
powerful poison, which, if the fruit be preserved whole, is liable to bo 
diffused through it. Fruits are preserved either with or without 
sugar ; if without, a quarter of a pint of water should be poured over 
every quart of fruit while in the can. If the fruit is to be sweetened, 
make a sirup, and pour on it in the can, until it is nearly full. A 
sirup for summer fruits is made by adding a pound of crushed sugar 
to a pint of water, and boiling two minutes. Yery acid fruits, such 
as quinces and plums, require a stronger sirup, say 1| lb. sugar to a 
pint of water. If the cans are not perfectly tight when the steam 
condenses within, forming a vacuum, the external pressure of the air 
may drive the soft beeswax in through the crevice. Aliments well 
put up will keep in a room at any temperature ; if the cans bulge, it 
is a sign of development of gas by internal decomposition, and their 
contents will not keep. 

3, PfiESEEVATIOlSr AT LOW TeMPEEATTJEES. 

583. Iniucnce of Temperatnre. — Degrees of temperature exert an 
absolute control over the duration of alimentary compounds. At 32** 
their juices are congealed, and they remain totally unchanged. At a 
few degrees above the freezing point changes are very slow. As we 
ascend the scale, the conditions of mutation become more favorable, 
except in the case of albumen, which is rendered more enduring by 
the heat of coagulation. In all other cases decomposition proceeds 
more rapidly as warmth increases, until the point of quick disorgani- 
zation, charring, and active combustion is reached. 

584. Freezing as a means of Preserving. — Congelation, therefore, may 
be resorted to as a means of preservation, chemical action being im 
possible where the substance is reduced to a solid state. Eemarkable 
cases are on record in which the bodies of animals have been disen- 
tombed from masses of ice, in such a state of preservation that the 
flesh was fit to support nutrition, although they had been wrapped in 
ice for such a vast period that the race to which they belonged had 
become extinct. It is customary in many regions to preserve fresh 
meat by freezing it, and packing in snow. Some object that the 
flavor of meat is injured by freezing ; but the Russians, on the con- 
tr^ry, insist that it is improved. Great care is necessary in thawing 
all frozen aliments, whether meat, fish, or vegetables. It should be 
done slowly, and the best way is by immersion in very cold water. 



AT LOW TEMPERATURES. 



307 



A shell of ice will be formed around them, as we have often seen in 
' taking the frost out of apples ; ' — the water in contact with the sur- 
face being frozen into a scale, by parting with its heat to thaw the 
frozen apple within. If thawed too rapidly, as by placing them in a 
warm room or in hot water, the taste is impaired, and the composition 
of the substance so afifected that putrefaction is rapidly brought on. 
One of the effects of freezing and thawing potatoes and some fruits, 
is to increase the amount of sugar, as shown by their sweeter taste. 

585. Low Temperatures above Freezing — Refrigerators. — We command 
.ow temperatures by cellars, and the use of ice. Excavations made 
below the surface of the ground have a temperature common to the 
surrounding strata of earth, which is cooler the deeper we go for 
nearly a hundred feet. The temperature is also very constant, the 
extremes of winter and summer being both excluded. The temper- 
ature of good cellars (40° to 60°), is below the range most favorable 
to putrefaction (60° to 100°). By the use of ice in the ice-house 
or refrigerator, the temperature 
may be kept down to within 5° 
or 10° of freezing. At these 
points changes proceed slowly, so 
that meat admits of being kept at 
this degree of coolness for a con- 
siderable time. It is said that 
meat should never be suffered to 
touch ice, as it is toughened and 
otherwise injured. The refriger- 
ator is commonly a rude, shelved 
box. If opening at top, it is 
troublesome of access and diflBcult 
to make its space available. If it 
have doors at the sides, the cold 
air flows out every time it is 
opened ; and if the ice is placed 
at the bottom, there is no circu- 
lation of air or means of cooling 
the upper space. A. S. Lyman, of N. Y., has obviated these defects by 
a newly devised arrangement (Fig. 107). The ice is placed in an upper 
chamber over a grate opening to the flue a, through which, ice-cold 
air constantly falls. The body of the refrigerator is occupied by three 
drawers, h c d, c being represented as partially withdrawn. TJie cold 
air fills these di-awers, and as it becomes slightly warmer is pressed 




Lyman's Bureau Befrigerator. 



808 PBESERVATION OF ALIMENTARY SUBSTANCES. 

upward in the direction of the arrows, and re-cooled hy contact with 
the ice. It descends again through the flue, the temperature of the 
■whole refrigerator being thus kept down nearly to freezing. The 
waste water is caught at g. The arrangement of drawers makes the 
whole space available, and is as convenient as a common bureau. 
When one is partially withdrawn, as at e, the air in, it being heavier 
than that of the room, does not escape, while the circulation of air con- 
tinues within. There is also a twofold means of purifying the air. 
At f there is a filter consisting of a wire-gauze box, through which 
the air passes and is disinfected. When it comes in contact with the 
ice, it is condensed and its moisture deposited, so that it has a real dry- 
ing eftect upon the articles to be preserved. The water constantly form- 
ing by the melting ice is highly absorbent of the gases set free by de- 
composing food, so that these impurities are constantly washed out of 
the air in its progress. The charcoal filter, in effect, divides the space 
into two refrigerators ; thus preventing articles in one from smelling or 
tasting of those in the other. Cars are constructed upon this prin- 
ciple, in which meat is transported from the Western States to New 
York in summer. 

586. Keeping Frnits at low Temperatnres. — The most important fact 
relating to the composition of fruits is the large proportion of water 
they all contain, and which constitutes the bulk of their peculiar 
juices. From three-fourths to nine-tenths of them being liquid, we 
are to regard them as consisting of a small amount of solid matter 
diffused through from four to ten times their bulk of water. This con- 
dition is eminently favorable to the action of fruits upon the organs 
of taste in their natural or uncooked state ; being in a kind of pulpy, 
half-dissolved condition, they are ready to take prompt effect upon 
the pappilae of the mouth. But the same property of fruits which 
adapts them so perfectly to our gustatory enjoyment, shortens the 
time when they can be so employed. Their abounding moisture 
favors decomposition, and they are hence perishable and short-lived. 
Yet by proper management fruits may be long preserved in a fresh 
and perfect state. Vegetables and juicy fruits, as apples and pears, 
can be preserved for months in cellars where the necessary warmth 
for inducing decay is not attained. Sometimes fruit, as many varieties 
of apples, are not really ripened at the time of gathering, but undergo 
a slow change during the winter months, their acid principle being 
converted into sngar. To be best preserved fruit should be picked whea 
perfectly dry, at a time when the stalk separates easily from the spur. 
Apples and pears should have their stalks or " stems " separated from 



BY DEYING. 309 

the tree, and not from themselves. The utmost care should be ob- 
served to prevent bruises or contusions ; some have implements for 
collecting the most valuable kinds of fruit, so as not to touch it with 
the hand. The most delicate kinds do not bear handling or wiping, 
as this rubs off the bloom which, when allowed to dry on some fruits, 
constitutes a natural varnish, closing up the pores and preventing the 
evaporation of the juices. Apples have been preserved a year in a 
fine fresh condition, by keeping them in an atmosphere within ten. 
degrees of the freezing point. Constancy of temperature is important, 
as alternations of heat and cold, by contracting and expanding the 
juices, seem to favor chemical changes. Grapes, cherries, currants, 
gooseberries, and other soft fruits have been preserved for use in win- 
ter by gathering them when not too ripe, and when very dry putting 
them unbruised into dry bottles, which are afterwards well corked, 
and then buried in the earth. The efficiency of this method of pre- 
serving is increased by immersing the bottles containing the fruit for 
a few minutes previously to corking, in hot water, which coagulates 
the vegetable albumen. The preservation is here due to the joint in- 
fluence of exclusion of air, and a low and uniform temperature. A 
preservatory for fruit, or kind of refrigerator on a large scale, has been 
devised by Mr. Paekeb. The fruit, picked carefully and unbruised, is 
conveyed at once to the preservatory, where the temperature is 
down nearly to freezing. The plan requires that ice be supplied the 
previous winter. 

4. Preseevatiox by DRTraa. 

587. Retentioa of Water in Fruits and Vegetables. — As nature places 
water in large quantities in organic bodies, in many cases she 
takes due precautions to keep it there. Unripe potatoes and unripe 
apples removed from the parent stock shrivel, shrink, and perish. 
These effects result from the porous condition of the immature skin, 
which permits the water within to escape by evaporation. " But 
when ripe this porous covering has become chemically changed into a 
thin impervious coating of corTc, through Vhich water can scarcely 
pass, and by which, therefore, it is confined within for months to- 
gether. It is this cork layer which enables the potato to keep the 
winter through, and the winter pear and winter apple to be brought 
to table in spring of their full dimensions." — (JonNSTON). 

588. Loss of Water as a means of Preservation. — Yet as organic sub- 
stances may bo kept by solidifying the water, that is, freezing them, 
they may also be preserved by withdrawing it. Both vegetable and 
animal substances are extensively preserved in this way. Drying is a 



310 PEESEKVATION OF ALIMENTARY SUBSTANCES. 

kind of disorganization of tlie alimentary body, its largest constituent 
being removed ; yet, in tbis case, the lost ingredient may be added 
again, and the substance brought into a condition more or less re- 
sembling the natural state. Drying is effected either by simple 
exposure to the sun and air, or by artificial heat of a higher intensity, 
applied in various ways. Both methods are quite practicable, but 
have their disadvantages. Drying in the air is necessarily a slow pro- 
cess, so that there is danger of moulding and fermentation ; the sub- 
stances require to be made small or thin, and as the air itself is moist, 
the drying can never be complete, but only reaches a certain point, 
and then fluctuates with the varying atmospheric dampness. On the 
other hand, when artificial heat is employed, as in kUn-drying in close 
apartments, it is obvious that the" foods are liable to be much altered 
in their nature. The starch may be dissolved, or altered to gum ; the 
sugar browned and changed to caramel, acquiring a bitter, disagree- 
able taste, if the heat of the drying chamber be too high ; while if the 
temperature be not higher than 140°, the albumen may be dried so as 
to dissolve again in water ; if higher, it is coagulated, and remains 
insoluble. 

589. Preserviag Saccnlent Vegetables. — These, if exposed to the air, 
evaporate their moisture, wilt, and lose their crisimess and freshness. 
A damp cool place is best to prevent these changes for a time. Many 
are kept soundly during winter by burying in the earth. M. Massoij, 
bead gardener to the Horticultural Society of Parir., has described a 
mode of preserving succulent vegetables by drying and compression. 
He prepares cabbage, cauliflower, potatoes, spinach, endive, celery, 
parsley, &c., in such a manner that they keep for any length of time, 
and when soaked in water resume much of their original freshness 
and taste. They are chiefly prepared for marine consumption. The 
packages of dried vegetables are covered with tinfoil. Dr. Hassall 
speaks of a specimen of dried cabbage as follows : " On opening the 
package the contents, which formed a solid cake, were seen to consist 
of fragments of leaves of ^ yellowish color, interspersed here and 
there with some that were green. In this state it was difficult to de- 
termine what the nature of the vegetable was. Soaked in hot water 
for about half an hour, it gradually underwent a great expansion, so 
that it acquired several times its former bulk. "When examined, it 
was evident at a moment's glance that the vegetable consisted of the 
sliced leaves of the white-heai*ted garden cabbage, presenting the ap- 
pearance and color, and possessing the taste and smell, to a remarkable 
extent, of the vegetable in its recent state." 



BY ANTISEPTIC AGEiO'S. 311 



5. Peeseevation by Antiseptics. 

690. Remarkable properties of common Salt. — Antiseptics are op- 
posers of putrefaction. Certain bodies when added to organized 
substances, possess the power of resisting or preventing their putre- 
factive decomposition ; they are numerous, and act in various ways. 
Those used for preserving aliments are salt-petre, sugar, alcohol, 
creosote, vinegar, oil, and common salt. However ' common ' this 
last substance may be, we shall nevertheless be interested in giving it a 
moment's attention. Though mild and pleasant to the taste, it is 
composed of two elements, one a yellowish green, suffocating, poison- 
ous gas, chlorine, and tlie other a bright silvery-looking metal, sodium 
(hence the chemical name of the substance chloride of sodium). 
When these two elements are brought together, they unite spontane- 
ously ; and yet so prodigous is the force with which they combine, so 
enormous the condensation of matter, that although the sodium unites 
with more than five hundred times its bulk of the heavy gas, yet the 
compound foi-med occupies less space fig. los. 

than the solid sodium alone did before 
the union. No known mechanical forc6 
could have accomplished this, yet it re- 
sults from the agency of chemical af- 
finity (Faeeaday). If a lump of com- 
mon salt, (it occurs in large masses in ■; 
the shape of roch salt,) be cut into the = 
form of a thin plate, and held before a 
fire, it does not stop the heat-rays, but ^^ 
has the singular property of permitting ^= 
them to dart through it, as light does 
through glass — it is the glass of heat. A 
hundred lbs. of water, hot or cold, dis- 
solve 37 of salt, forming a saturated so- 
lution or the strongest brine. Wlien the 
briny solution evaporates, the salt reap- 

„„„ • J.1 V 1 r J. IT How crystals of common salt are 

pears m the solid form, or crystallizes, ■' formed. 

Its crystals are cube shaped ; if the evaporation takes place slowly 
they are large, but if it be rapid, they are small, and formed in a 
curious manner. Resulting fi-om evaporation, they are naturally 
formed at the surface of the liquid, and present the appearance of little 
floating cubes, as shown in (Fig. 108), where the solid crystal is up- 
borne or floats in a little depression of the fluid surface. New crystals 




312 PEESEKVATION OF ALIMKNTAEY SUBSTANCES. 

eoon form, which are joined to the first at its four upper edges, con 
Btituting a frame above the first little cube (Fig. 109). As the whole 
descends into the fluid, new crystals are grouped around the first 
frame constituting a second {Tig. 110). Another set added in the 
same way gives the appearance shown in Fig 111. The consequence 
of this arrangement is that the crystals are grouped into hollow, four- 
sided pyramids, the walls of which have the appearance of steps, be- 
cause the rows of small crystals retreat from each other. This mode 
of grouping is called hopper-shaped (Fig. 112), 

591. Sources and Porification of Salt. — Salt is obtained from three 
sources ; first^ it is dug from the earth in mines, in large masses, like 
transparent stones {roch salt) ; second^ it is procured by evaporating 
sea-water (bay salt) ; and, third, by boiling down the liquid of brine 
springs. It differs very much, in purity, from different sources, being 
in many cases contaminated by salts of calcium and magnesium, which 
render it bitter. Pure salt, in damp weather, attracts water from the 
atmosphere, and becomes moist, but parts with it again when the 
weather becomes dry. But the chlorides of calcium and magnesium 
are much more absorbent of water, and hence, if the salt is damp and 
moist when the air is dry, we may infer that a large proportion 
of these substances is present in it. Salt, for certain culinary pur- 
poses, as for salting butter, should be perfectly pure. Its bitter in- 
gredients are moi-e readily soluble in water than is the salt itself; 
hence, by pouring two or three quarts of boiling water upon ten or 
twenty lbs. of salt, stirring the whole well now and then for a couple 
of hours, and afterwards straining it through a clean cloth, the ob- 
noxious substances may be carried away in solution. Among the 
purest, is that called Liverpool salt, which is an English rock-salt dug 
from the mines ; dissolved, recrystallized and ground. 

592. How salt preserves meat. — Salt is more widely used than any 
other agent in conserving provisions, especially meats. It is well 
known that when fresh meat is sprinkled with dry salt, it is found 
after a few days swimming in brine, although not a drop of water 
has been added. If meat be placed in brine it grows lighter, while 
the quantity of liquid is increased. The explanation of this is, 
that Avater has a stronger attraction for salt than it has for flesh. 
Fresh meat contains three-fourths of its weight of water, which is 
held in it as it is in a sponge. Dry salt will extract a large part of 
this water, dissolving in it and forming a saline liquid or brine. In 
this case, the water of the meat is divided into two parts ; one is taken 
up by the salt to form brine, while the other is kept back by the 



BY ANTISEPTIC AGENTS. 313 

meat. The salt robs the meat of one-third or one-half the water of ita 
juice. Salting is therefore only an indirect mode of drjdng ; the chief 
cause, perhaps, of the preservation of the meat, being, that there is 
not sufficient water left in it to allow putrefaction. The surrounding 
brine does not answer this purpose, as it does not act upon the meat ; its 
relation to flesh being totally different to that of fresh water. If fresh 
water be applied t6 a piece of dry meat, it is seen to have a strong 
attraction for it, but if we use even a weak solution of salt, it flows 
over it wetting it but very imperfectly. 

593. now meat is injured by salting. — The separation of water from 
the fibre of meat shrinks, hardens, and consequently renders it less di- 
gestible. It is quite probable, also, that the salt, in some way not yet 
understood, combines with the fibre itself, thus altering injuriously 
its nutritive properties. Peeeiea thinks that the separation of water 
is not sufficient alone to account for its preservative action, but that 
it must produce some further unexplained effect upon the muscular 
tissue. The main and well-established injury of salting, however, is 
caused by the loss from the meat of valuable constituents, which escape 
along with the water which the salt withdraws. It has been shown 
that the most influential constituents of meat are dissolved in its juice 
(471). The salt, therefore, really abstracts the juice of flesh with its 
albumen, kreatine, and valuable salts ; in fact, the brine is found to 
contain the chief soup-forming elements of meat. Salting, therefore, 
exhausts meat far more than simple boiling, and as the brine is not 
consumed, but thrown away, the loss is still greater In salting meat, 
however, there happens to be a slight advantage resulting from its 
impurities, lime and magnesia. These are decomposed by the phos- 
phoric acid of the juice of flesh, and precipitated upon the surfiice, 
forming a white crust, which may often be observed upon salt meat ; 
this constituent, therefore, is not separated in the brine. Saltpetre 
has a preservative effect, probably in the same way as common salt, 
but it is not so powerful, and unlike salt produces a reddening of the 
animal fibres. A little of it is often used along with salt for this 
purpose. 

594. Salting Vegetables. — These may be preserved by salt, as well as 
flesh, but it is not so commonly done. In salting vegetables, however, 
a fermentation ensues, which gives rise to lactic acid. This is the 
case in the preparation oi sauerkraut from cabbages, and in salting cu- 
cumbers. The brine with which both vegetables are surrounded ig 
found strongly impregnated with both lactic and butyric acids. 

595. Preservation by Sogar.— This is chiefly employed to preserve 
14 



314 PRESEEVATION OP ALIMENTARY SUBSTANCES. 

fruits. Many employ botli sugar and molasses for tlie preservatio"ii of 
meat ; sometimes alone, but more commonly united with salt. Tha 
principle of preserving by means of sugar is probably similar to that 
of salting. In the case of fruits, the sugar penetrates within, changing 
the juices to a sirup, and diminishing their tendency to fermentation 
or decomposition. TVeak or dilute solutions of sugar are, however, 
very prone to change ; they require to be of a thick or sirupy consist- 
ence. Knapp states that the drops of water which condense from 
the state of vapor on the sides of the vessels in which the preserves 
are placed, are often sufficient to induce incipient decomposition, by 
diluting the upper layers of sugar. The effect of the acids of fruits is 
gradually to convert the cane sugar into uncrystallizable and more fer- 
mentable grape sugar. 

596. Preserving by Alcohol and other substances. — Strong alcoholic li- 
quors are used to prevent decomposition in both vegetable and animal 
bodies. They penetrate the substance, combine with its juices, and 
as the organic tissues have less attraction for the spirituous mixture, 
it escapes ; and the tissues themselves shrink and harden in the same 
way as when salted. Alcohol also obstructs change by seizing upon 
atmospheric oxygen, in virtue of its superior attraction for that gas, 
and thus preventing it from acting upon the substance to be preserved. 
Vinegar is much used for preserving, but how it acts has not been ex- 
plained. Spices exert the same influence. Creosote, a pungent com- 
pound existing in common smoke, and which starts the tears when 
the smoke enters the eyes, is a powerful antiseptic, or preventer of 
putrefaction. Meat dipped for a short time in a solution of it will not 
putrefy, even in the heat of summer. Or if exposed in a close box to 
the vapor of creosote, the effect is the same, though in both cases the 
amount producing the result is extremely small. The preservative 
effect of smoke-drying is partly due to creosote, which gives to the 
meat its peculiar smoky taste, and partly to desiccation. Oil is but 
little employed in saving alimentary substances — two kinds of fish, 
anchovies and sardines, are preserved in it. Charcoal has always been 
ranked as an antiseptic or arrester of putrefaction ; but it has been 
lately shown that it is rather promotive of decomposition. How this 
is, wUl be explained in another place (811). 

6. Preservation of Milk, Butter, and Cheese. 

597. Modes of preserving Milk. — The cause of the souring of milk 
we have seen to be the action of oxygen upon its casein, which altera 
the sugar to acid (54Y). If, therefore, the milk be tightly bottled, and 



MILK, BUTTEK, AND CHEESE. 315 

then boiled, the fermentative power of the curdy matter is destroyed, 
and it may be kept sweet for several months. "When, however, the 
milk is again exposed to the air, the curd resumes its power of acting 
upon sugar, and acid is again formed. "When milk is kept at a 
low temperature, the cold retards its changes. If the vessels contain- 
ing it are placed in a running stream of cool water, or in a place cooled 
by ice, it will remain cool for several days. Milk may also be pre- 
vented from souring, even in warm weather, by adding to it a little 
soda or magnesia. The alkali destroyes the acid as fast as it is pro- 
duced, and the liquid remains sweet. The small quantity of lactate 
of soda or magnesia which is formed, is but slightly objectionable. If 
mUk be evaporated to dryness, at a gentle heat, with constant stirring, 
it forms a pasty mass, which may be long kept, and which reproduces 
mUk when again dissolved in water. Alden's concentrated milk is a 
solidified pasty preparation, made by evaporating milk, with sugar, 
and affords an excellent substitute for fresh milk, in many cases, when 
dissolved in water. 

598. Unpurified Butter quickly spoils. — Butter when taken from the 
churn contains more or less of all the ingredients of milk, water, casein, 
sugar, lactic acid, which exist in the form of buttermilk, diffused 
through the oily mass. Chevreijl states that fresh butter yields 16 
per cent, of these ingredients, chiefly water, and 74 of pure fat. In 
this state butter cannot be kept at all. Active decomposition takes 
place almost at once, the butter acquires a bad odor, and a strong dis- 
agrcQable taste. Tlie casein passes into incipent putrescence, generat- 
ing offensive compounds, from both the sugar and oily matter. 

599. Butter Purified by Mechanical Working. — It is obvious, therefore, 
that in order to preserve butter, it must first be freed from its butter- 
milk, which is done by working it, over and over, and pressing or 
squeezing it, which causes the liquid slowly to ooze out and flow away. 
The working or kneading is done with a wooden ladle, or a simple 
machine adapted to the purpose, or else by the naked hand. It is ob- 
jected that the employment of the hand is apt to taint the butter by 
its perspiration ; but while it is admitted that moist hands should never 
do the work, many urge that those which are naturally cool and dry, 
and made clean by washing in warm water and oatmeal {not soap), 
and then rinsed in cold water, will remove the sour milk from the 
butter more effectually than any instrument whatever, without in the 
least degree injuring it. Overworking softens butter, renders it oily, 
and obliterates the grain. 

600. Preparation of Butter by Washing. — Some join washing with 



316 PBESERVATION OF ALIALENTABY SUBSTANCES. 

mechanical working, to separate the buttermilk. It is objected to this, 
first, that water removes or impairs the fine aroma of the butter, and, 
tecond., that it exposes the particles of butter to the injurious action 
of air much more than mechanical working. On the other hand, it ia 
alleged that Avithout water we cannot completely remove the ferment- 
ing matter, the smallest portion of which, if left in the butter, ulti- 
mately injures it. If water be used, it is of the utmost consequence to 
guard against its impurities. It is liable to contain organic substances, 
vegetable or animal matter, in solution, invisible, yet commonly pres- 
ent, even in spring water. These the butter is sure to extract, and 
their only effect can be to injure it. The calcareous waters of lime- 
stone districts are declared to be unfit for washing butter. Speengel 
states that the butter absorbs the lime, and is unpleasantly affected by 
it. A. B. DicKiNSOiT is of opinion that the best butter cannot be 
made where hard water is used to wash it ; he employs only the soft- 
est and purest for this purpose. 

601. Cause of Rancidity in Bnttcr. — Pure oil has little spontaneous 
tendency to change. If lard, for example, be obtained in a condition 
of purity, it may be kept sweet for a long time without salt, when 
protected from the air. Tiiat it does alter and spoil in many cases, is 
owing to traces of nitrogenous matter, animal membranes, fibres, &c., 
which have not been entirely separated from it. These pass into de- 
composition, and carry along the surrounding oUy substance. So with 
butter ; when pure, and cut off from the air, it may be long kept with- 
out adding any preservative substance. But a trifling amount of curd 
left in it is sufficient to infect the whole mass. It is decomposed, and 
acting in the way of ferment upon the sugar and oily substance itself, 
develops a series of acids, the butyric, which is highly disagreeable 
and offensive, and the capric and caproic acids, which have a strong 
sour odor of perspiration. The butter is then said to be rancid. 
In general, the more casein is left in butter, the greater is its tendency 
to rancidity. 

602. Action of Air upon Batter. — The fat of butter is chiefly composed 
oi margarin, which is its main solidifying constituent, and abounds 
also in human fat. It is associated with a more oily part, olein. 
Now, air acts not only upon the curdy principle, causing its putres- 
cence ; but its oxygen is also rapidly absorbed by the oleic acid. One 
of the effects of this absorption may be to harden it, or convert it into 
margaric acid. This is, however, a first step of decomposition, which, 
when once begun, may rajndly extend to the production of various 
offensive substances. "When, therefore, butter is much exposed to the 



MILK, BUTTER, AND CHEESE. 317 

air it is certain to acquire a surface rancidity, which, without pene- 
trating into the interior, is yet sufficient to injure its flavor. It is in- 
dispensable to its efiectual preservation that the air be entirely ex- 
cluded from it. Hence, in packing butter, the cask or firkin should 
be perfectly air tight. Care should- be taken that no cavities or spaces 
are left. If portions of butter are successively added, the surface 
should be either removed or raised up in furrows, that the new portion 
may be thoroughly mixed with it, or it should be kept covered with 
brine, and the vessel ought not to be finally closed until the butter has 
ceased shrinking, and the vacancies that have arisen between the but- 
ter and vessel's sides are carefully closed. 

603. Sabstfinces used to preserve Butter. — Salt, added to butter, per- 
forms the twofold office of flavoring and preserving it. The salt be- 
comes dissolved in the water contained in it, and forms a brine, a 
portion of which flows away, while • the butter shrinks and becomes 
more solid. Salt preserves butter by preventing its casein from chang- 
ing ; hence the more of this substance is left in it the rcore need of 
salt. The quantity used is variable, from one to six drachms to the 
pound of butter. It is objected to salt that it masks the true flavor 
of butter, especially if it be not of the purest quality (591). Salt- 
petre will preserve butter; but it is less active than common salt, 
and some think its flavor agreeable. Sugar is sometimes added to aid 
in preservation, and to compensate for the loss of the sugar of milk. 
Honey has been also used for the same purpose, at the rate of an 
ounce to the pound of butter. Some employ salt, saltpetre, and sugar 
all together. From an examination of upwards of forty samples of 
English butter, Hassall found the proportion of water in them to 
vary from 10 to 20, and even 30 per cent,, and the proportion of salt 
from one to six or seven per cent. A simple method of ascertaining 
the quantity of water in butter is, to melt it and put it in a small bottle 
near the fire for an hour. The water and salt will separate and sink 
to the bottom. 

604. Changes of Cheese by Time. — Cheese requires time to develop 
its peculiar flavor, or ripen. A slow fermentation takes place within, 
which differs much according to the variety of circumstances con- 
nected with its preparation, and the degree and steadiness of the tempe- 
rature at which it is kept. The fermentation, which is gentle and pro- 
longed at a low temperature, becomes too rapid in a warm, moist plate. 
The influence of temperature is shown by the fact that in certain locali- 
ties of France, especially at Roquefort, there are subterranean caverns 
which rent and are sold at enormous sums for the purpose of keeping 



318 MATERIALS OF CULINARY AND TABLE UTENSILS. 

and maturing cheese. These natural rock-cellars are maintained, bj 
gentle circulation of air, at 41" to 42°. The nature of the changes 
that cheese undergoes has not been clearly traced. It is known that 
the casein becomes so altered as to dissolve in water. The salt intro- 
duced to preserve it is said to be decomposed ; the oily matter gets 
rancid, as may be shown by extracting it with ether; and peculiar 
volatile acids and aromatic comjiounds are produced. Cheese of poor 
or inferior flavor, it is said, may be inoculated with the peculiar fer- 
mentation of a better cheese, by inserting a plug or cylinder of the 
latter into a hole made to the heart of the former. To prevent the 
attacks of insects the cheese should be brushed, rubbed with brine or 
salt, and smeared over with sweet oil, the shelves on which they rest 
being often washed with boiling water. 

605. Preservation of Eggs. — When t ewly laid, eggs are almost per- 
fectly full. But the shell is porous, and the watery portion of its 
contents begins to evaporate through its pores the moment it is ex- 
posed to the air, so that the eggs become lighter every day. As the 
water escapes outward through the pores of the shell air passes inward 
and takes its place, and the amount of air that accumulates within de- 
pends, of course, upon the extent of the loss by perspiration. Eggs 
which we have preserved for upward of a year, packed in salt, small 
ends downwards, lost from 25 to 50 per cent, of their weight, and did 
not putrefy. As the moisture evaporated the white became thick 
and adhesive, and the upper part was filled with air. To preserve 
the interior of the egg in its natural state, it is necessary to seal up 
the pores of the shell air-tight. This may be done by dipping them in 
melted suet, olive oil, milk of lime, solution of gum arable, or cover- 
ing them with any air-proof varnish. They are then packed in bran, 
meal, salt, ashes, or charcoal powder. EEAirMUE is said to have coated 
eggs with spirit varnish, and produced chickens from them after two 
years, when the varnish was carefully removed. 

VI.— MATERIALS OF CULINARY AND TABLE UTENSILS. 

606. It seems important in this place to oflTer some observations 
pertaining to our ordinary kitchen and table utensils. We speak of 
the chemical properties of their materials rather than of their mechan- 
ical structure. 

607. Utensils of Iron, — Iron is umch employed for vessels in kitchen 
operations. The chief objection to it springs from its powerful attrac- 
tion for oxygen, which it obtains from the atmosphere. It will even 



VESSELS OF IKON AND TIN. 319 

decompose water to get it. la consequence of this strong tendency to 
oxidation, its surface becomes corroded and roughened by a coating of 
rust, -which is simply oxide of iron. The rust combines with various 
substances contained in food, and forms compounds which discolor the 
articles cooked in iron vessels, and often impart an irony or styptic 
taste. Fortunately, however, most of these compounds, although ob- 
jectionable, are not actively poisonous ; yet, sulphate of iron (copperas) 
and some other mineral salts of iron, are so. Cast iron is much less 
liable to rust than malleable, or wrouj^ht iron. There is one mode of 
managing cast iron vessels, by which the disagreeable eflFects of rust 
may be much diminished, if not quite prevented. If the inside of 
stew-pans, boilers, and kettles be simply washed and rinsed out with 
warm water, and wiped with a soft cloth instead of being scoured with 
sand or polishing materials, the vessel will not expose a clean metallic 
surface, but become evenly coated with a hard, thin crust of a dark 
brown color, forming a sort of enamel. If this coating be allowed to 
remain, it will gradually consolidate and at last become so hard as to 
take a tolerable polish. The thin film of rust thus prevents deeper 
rusting and at the same time remains undissolved by culinary liquids. 

609. Protection of Iron by Tin. — As such protection, however, in- 
volves care and consideration, it is uncertain and unsatisfactory, and 
besides it is inapplicable to vessels of thin or sheet iron. A better 
method is that of coating over the iron with metallic tin, Avhicli has 
come into universal use in the form of tin-toare. The sheet tin which 
is so widely employed for household utensils is made by dipping pol- 
ished sheet iron in vats of melted tin. Tin itself is a metal some- 
what harder than lead, but is never used for culinary vessels. "What 
is called iloch tin is generally supposed to consist of the pure metal. 
This is an error. It is only tinned iron plate, better planished, stouter, 
and heavier than ordinary. All tin ware, therefore, is only iron plate 
coated or protected by tin: yet, practically, it is the metallic tin only 
that we are concerned with, as that alone comes in contact with our 
food. 

610. Adaptation of Tin to Cnlinary Parposcs. — Tin, in its metallic 
state, seems to have no injurious effect upon the animal system, for it 
is often given medicinally in considerable doses, in the form of powder 
and filings. It is frequently melted off from the sides of sauce-pans or 
other vessels in globules, and is thus liable to be swallowed, a circum- 
stance which need occasion no alarm. The attraction of tin for oxy- 
gen is feeble, and it therefore oxidizes or rusts very slowly. Strong 
suiids, as vinegar or lemon juice, boiled in tin-coated vessels, may dis- 



320 MATERIALS OP CULINARY AND TABLE UTENSILS. 

solve a minute portion of the metal, forming salts of oxide of tin, 
but the quantity will he so extremely small that it need excite little 
apprehension. It is a question among tosicologists whether its oxide 
be jjoisonous. Proust showed that a tin platter, which had been in 
use two years, lost only four grains of its original weight, and probably 
the greater part of this loss was caused by abrasion with whiting, sand, 
or other sharp substances during cleansing. If half of it had been 
taken into the system dissolved, it would have amounted only to ^j of 
a grain per day, a quantity too trifling to do much harm, even if it were 
a strong poison. Common tin, however, is contaminated with traces 
of arsenic, copper, and lead, which are more liable to be acted upon 
by organic acids and vegetables containing sulphur, as onions, greens, 
&c. Peeeiea remarks that acid, fatty, saline, and even albuminous 
substances may occasion colic and vomiting by having remained for 
some time in tin vessels. Still, tin is unquestionably the safest and 
most wholesome metal that it is found practicable to employ 11 domes- 
tic economy. 

61 1. Zinc A'essels Objectionable. — Zinc is rarely employed as a mate- 
rial for culinary vessels. In many cases it would be unsafe, as a poi- 
sonous oxide slowly forms upon its surface. It has been recommended 
for milk pans on the ground that milk would remain longer sweet in 
them, and hence, more cream arise. But whatever power of kee^nng 
milk sweet zinc possesses, it can only be caused by neutralizing the 
acid of milk with oxide of zinc, thus forming in the liquid a poisonous 
lactate of zinc. 

612. Beliavior of Copper in contact with Food. — This metal suffers 
very little change in dry air, but in a moist atmosphere oxygen unites 
with it, forming oxide of copper ; and carbonic acid of the air, combin- 
ing with that substance, forms carbonate of copper, of a green color. 
Copper is easily acted on by the acid of vinegar, forming verdigris^ 
or the acetate of copper^ which is an energetic poison. Other vegeta- 
ble acids form poisonous salts with it in the same way. Common salt 
is decomposed by contact with metallic copper during oxidation, the 
poisonous chloride of copper being formed. All kinds of fatty and 
oily matter have the property of acting upon copper and generatfhg 
poisonous combinations. Sugar also forms a compound with oxide of 
copper, — the sacharate of copper. 

613. Test. — As the salts of copper are of a green color, vessels of 
this metal have a tendency to stain their contents green. They are 
sometimes employed purposely to deepen the green of pickles, &c., 
and cooks often throw a penny-piece into a pot of boiling greens to 



COPPER AND ENAMELLED VESSELS. 321 

intensify their color. A simple test for copper in solution is, to plunge 
into the suspected liquid a plate of polished iron, (a knife blade, for 
example,) when in a short time, (from five minutes to as many hours,) 
it will become coated with metallic copper. The solution ought to be 
only very slightly acid. Now, as acid, oil, or salt, is found in almost 
every article of diet, it is clear that this metal, unprotected, is quite 
unfit for vessels designed to hold food. 

614. Protection of Copper Utensils. — Yet copper has several advan- 
tages as a material for culinary utensils. It is but slowly oxidized, and 
hence does not corrode deep, scale, become thin, and finally fall into 
holes as iron vessels are liable to do. Besides, copper is a better con- 
ductor of heat than iron or tin plate, and consequently heats more 
promptly and with less fuel, and as it wears long, and the metal when 
old bears a comparatively high price, its employment, in the long run, 
is unquestionably economical. Copper vessels ought never to be used, 
however, without being thoroughly protected by a coating of tin and 
when this begins to wear ofi" they should be at once recoated, which the 
copper or tin-smith can do at any time. It has been stated that a small 
patch of tin upon the surface of a copper vessel would entirely prevent 
the oxidation of the latter by galvanic influence ; but Mr. Mitchel has 
shown by experiment that such is not the fact, and that the only 
safeguard is in covering completely the entire copper surface. Brass 
is an alloy of zinc and copper, and although less liable to oxidize, is 
nevertheless unsafe. Kettles of brass are often employed in preparing 
sauces, sweetmeats, &c., but this ought never to be done unless they 
are scrupulously clean and polished, and hot mixtures should not be 
allow.ed to cool or remain in them. 

615. Enamelled Ironware Vessels. — It would seem that no one mate- 
rial possesses all the qualities desirable to form cooking vessels. 
Some of the metals are strong and resist heat ; but, as we have seen, 
various kinds of food corrode them. Earthenware, on the contrary, 
if well made, resists chemical action, but is fractured by slight blows 
and the careless application of heat. An attempt has been made to 
combine the advantages of both by enamelling the interior of iron ves- 
sels with a kind of vitreous or earthenware glaze. Various cooking 
vessels, as saucepans, boilers, and the like, have been prepared in this 
manner, and answer an admirable purpose. Dr. Ure remarks, I con- 
sider such a manufacture to be one of the greatest improvements 
recently introduced into domestic economy, such vessels being remark- 
ably clean, salubrious, and adapted to the delicate culinary opera- 
tions of boiling, stewing, making of jellies, preserves, &c. 

14* 



322 MATERIALS OF CULINARY AND TABLE UTENSILS. 

616. Earthenware Vessels— Glazing. — Vessels of earthenware are in 
universal bouseliold use. They are made, as is well known, of clay 
and sand, of various degrees of purity, witk other ingredients, forming 
a plastic mass, which is moulded into aU required shapes, and hardened 
by baking in a hot furnace. The ware, as it thus comes from the 
baking process, is porous, and absorbs water. To give it a smooth, 
glossy, watei'-resisting surface, it is subjected to the operation oi glaz- 
ing. This is effected in two ways; first, when the stoneware has at- 
tained a very high temperature, a few handfuls of damp sea-salt are 
thrown into the furnace. The salt volatilizes, the vapor is decomposed, 
the hydrochloric acid escaping ; while the soda, diffused over the sur- 
face of the ware, combines with its silica, and glosses over the pieces 
with a smooth, hard varnish. Another mode by which the desired 
artificial surface is given to earthenware, is by taking it from the fire 
when it has become sufiiciently firm and stiff, immersing it in a pre- 
pared liquid, and restoring it again to the furnace, where by the action 
of heat a vitreous or glassy coating is formed. 

6 IT. Earthenware Glaze containing Lead. — The preparations employed 
for glazing common earthenware, are chiefly combinations of lead 
with the alkalies, producing vitreous or glassy compounds. It is 
known that lead enters largely into many kinds of glass ; it imparts to 
them great brilliancy and beauty, but makes them soft, so that they 
are easily scratched, and liable to be attacked by strong chemical sub- 
stances. Lead glaze upon earthenware is also subject to the same 
objection. It is tender and can be scraped off with a knife, so that 
the plates soon become marred and roughened. They also soon black- 
en, or darken, when in contact with sulphurized substances. Cooking 
eggs or fish in these vessels gives them a brownish tinge. If less lead 
be used, the glaze becomes less fusible, the process of applying it more 
difficult, and hence the ware more expensive. Lead glazing can be drv 
tected by its remarkably smooth, lustrous surface, resembling varnish ; 
while the salt glaze, on the contrary, has less lustre, and the vessel has 
not so fine an appearance, all the asperities of the clay beneath being 
perfectly visible. Fatty matters, and the acids of fruits, exert a solvent 
action on oxide of lead combined in lead glaze, especially where the 
chemical energy is increased by a boiling temperature. 

618. Other defects of Earthenware Glaze. — If a piece of earthenware 
be broken, we may observe upon the freshly fractured edge, the thin 
coating of glaze which has been fused on to the body of the ware. If 
the tongue be touched to the broken surftice, it will adhere, showing 
the porous and absorbent nature of the material. Now it often hap- 



EAKTHEN AND POKCKLAIIS" TV ABE. 323 

pens that the shell of glaze and the body which it encloses, are not 
affected in the same way by changes of temperature. They expand 
and contract unequally when heated and cooled, the consequence be- 
ing, that the glaze breaks or starts, and the surface of the plate, sau- 
cer, or vessel, becomes covered with a network of cracks. Ware in 
fjuch a condition is said to be crazed. Through these cracks liquid or- 
ganic matters are liable to be absorbed, which make the articles un- 
cleanly and impure. Glaze that does not crack is often too soft. To 
determine this, drop a small quantity of ink upon it, and dry before 
the fire, and then wash it thoroughly ; if the glaze be too soft, an in- 
delible brown stain wiU remain. 

619. How Porcelaia-ware is made. — Thjs is the purest and most per- 
fect product of the plastic art. We are indebted for several suggestions 
concerning its processes to Messrs. Haviland, of this city, whose ex- 
tensive establishment in France has afforded them a large experience 
in the porcelain manufacture. This ware was first made in China, and is 
still known as China-ware. But, after long and difficult experience, the 
manufacture has at length become so perfected in Europe as greatly 
to surpass the Chinese in elegance, and hence but little is now import- 
ed from that country. True porcelain consists of two essentially dif- 
ferent constituents, one of which is an infusible, plastic, white clay, 
called kaolin, or China-clay, and the other an infusible but not plastic 
substance, called the flux, which is composed of the mineral felspar. 
Kaolin alone would afford a porous, opaque body ; the flux, however, 
softens in the heat of the baking furnace, and penetrates as a vitreous 
or glassy matter the whole body of the clay, completely filling up tlie 
pores, and covering all the surface; it binds the whole together into 
a dense impenetrable mass. Porcelain-ware is translucent, or permits 
the partial passage of light, which is due to the clay body being satu- 
rated as it were with glass, as transparent paper is permeated with 
oil. The material is moulded with great care and nicety into the de- 
sired forms, and then, placed in cases of clay made expressly to hold 
and protect them, are put into the kiln or furnace, and subjected to 
an intense heat for 15 or 20 hours. The articles are then withdrawn 
and dipped into a glaze composed of felspar, of the same nature as 
the flux, and which never contains either lead or tin. The ware is 
then returned to the furnace and subjected to the most intense white 
heat that art can produce, for 10 or 20 hours longer. The glaze is 
thus melted into the flux, so that the porcelain has a uniform body, as 
we see when it is broken. There is no accurate mode of measuring 
the very high ten)perature8 produced in these kilns, but by the method 



824 rHYSIOLOGICAL EFFECTS OF FOOD. 

adopted, the heat is estimated to i"un up to 21,000 degrees of the 
Fahrenlieit scale. The color of porcelain is milk-white, without any 
tinge of blue. The qualities which give it pre-eminence among tha 
clay wares, are the entire absence of porosity, the intimate union of 
the glaze with the mass, and the indestructibleness of the glazed sur- 
face under the knife, or when exposed to changes of temperature, and 
various chemical agencies. The production of the naked porcelain- 
ware in its present perfection, is one of the most signal triumphs of 
inventive ingenuity and perseverance, which the history of domestic 
improvement affords. But when we observe the beautiful and deli- 
cate colors with which porcelain is now ornamented, we ai*e aston- 
ished at the resources of art. The paints or pigments with which ex- 
quisite pictures are made upon it, consist of colored glass, stained of 
various hues by metallic oxides. The coloring materials require to be 
fire-proof, as they are pamted upon the ware, and then melted into the 
flux or glaze by the heat of the furnace. 

620. Repairing broken Porcelain. — Various cements are in use for 
producing adhesion between fragments of broken porcelain and glass. 
A very strong cement for common earthenware is made by boiling 
slices of skim-milk cheese with water into a paste, and then grinding 
it with newly slaked lime in a mortar. "White of egg will cause a 
quite strong adhesion, where the objects are not exposed to moisture. 
It is however improved by mixture with slaked lime. Shellac dis- 
solved in alcohol or in a solution of borax, forms a pretty good ce- 
ment. Various excellent cements are to be procured, ready prepared, 
of the dealers. In their anxiety to unite the fragments strongly, per- 
sons are apt to defeat their purpose by appljang the cement too thick- 
ly, whereas the least possible quantity should be used, so as to bring 
the edges most closely together. This may be aided by heating tho 
fragments to be joined, 

VII.— PHYSIOLOGICAL EFFECTS OF FOOD. 
1. Basis of the Demand foe Aliment. 

621. Creation a Continnons Work. — We are accustomed to conceive 
of the creation of man as a dim miraculous event of the most ancient 
time, half-forgetting that God's scheme of managing the living world 
is one ofperjjetual creation. Had our earth been formed of an eternal 
adamant, subject to no vicissitudes of change through f^ll the cycles of 
duration, we might perhaps well refer to the act of bringing it into 
existence, as especially illustrative of creative power. But where all 



BASIS OF THE DEMAND FOB ALIMENT. 325 

is changing, transitory, and incessantly dissolving away, so that noth- 
ing remains immutable, but God's conception of being, which the 
whole universe is for ever hastening to realize, we cannot escape the 
conviction of his immediate, living, omnipresent, constructive agency. 
Tlie truth is, we are hourly and momentarily created, and it is impos- 
sible to imagine in what respect the first act of formative power was 
more wonderful or glorious, or afforded any more conspicuous display 
of omnipotent wisdom, than that august procession of phenomena by 
which man, and the entire living world, are now and continually 
called into being. Those material atoms which are to-day interposed 
between us and destruction, are recent from chaos, — they Avere but 
yesterday formless dust of the earth, corroded and pulverized rocks, 
or fleeting and viewless gases of the air. These, through the vast 
enginery of astronomic systems, whose impulses of movement spring 
directly from the Almighty Will, have entered a world of organic or- 
der, are wrought into new states, and made capable of nourishing the 
animal body. The mingled gases and mineral dust, have become 
vital aliment. The test-miracle which the Tempter of old demanded 
a^ evidence of Godlike Power, is disclosed to the eye of science, as a 
result of natural laws, for in the most literal sense, " stones are made 
bread." 

622. Our Systems capable of being nnderstood. — That it was tesigned 
for us to understand what goes on within the body, we are not at 
liberty to doubt. Instead of being the theatre of a mysterious power 
which defies investigation, we find the living system acting under 
allegiance to invariable laws, and entirely amenable to investigation. 
The wiiolo course of physiological discovery has consisted in showing 
that the human constitution is an embodiment and illustration of 
reason. The victory of research is to understand a thing ; that is, to 
bring it into agreement with reason. The mechanism of the eye was 
a mystery, until its optical adaptations and purposes were discovered ; 
that is, the reason of its construction. The heart was an object of 
mere curious wonder and superstitious speculation, until the circula- 
tion was discovered, when the reasonaMe vscs of its parts were at 
once understood. The whole scope and drift of past inquiry, and all 
the considerations which cluster around the subject, lead us to expect 
and demand a rational explanation of living processes. " Not many 
years ago, the most acute and distinguished physicans regarded the 
Btomach as the abode of a conjurer ; who, if respectfully treated, and 
in good humor, can change thistles, hay, roots, fruits, and seeds, 
into blood and flesh; but when angry, despises, or spoils the best 



32G PHYSIOLOGICAL EFFECTS OF FOOD. 

food." Chemistry has dispelled these crude fancies, and enabled U8 
to understand how such marvellous transformations occur. We are 
getting daily clews to the profounder secrets of the organism ; know- 
ledge is here as rapidly progressive as in any other department of 
science. In this connection Dr. Draper remarks, " Since it is given 
us to know our own existence, and be conscious of our own individu- 
ality, we may rest assured that we have what is in reality a far more 
wonderful power, the capacity of comprehending all the conditions 
of our life. God has formed our understanding to grasp all these 
things. For my own part, I have no sympathy with those who say of 
this or that physiological problem, it is above our reason. My faith 
in the power of the intellect of man, is profound. Far from suppos- 
ing that there are many things in the structure and functions of the 
body which we can never comprehend, I believe there is nothing in it 
that we shall not at last explain. Then, and not till then, will man 
be a perfect monument of the wisdom and power of his Maker, a 
created being knowing his own existence, and capable of explain- 
ing it." 

623. The liymg System a theatre of change. — The body of the grown 
man presents to us the same unaltered aspect of form and size, for 
long periods of time. With the exception of furrows deepening in 
the countenance, an adult man may seem hardly to alter for half a 
hundred years. But this appearance is altogether illusory ; for with 
apparent bodily identity, there has really been an active and rapid 
change, daily and nightly, hourly and momently, an incessant waste 
and renewal of all the corporeal parts. A waterfall is permanent, and 
may present the same aspect of identity, and unchangeableness from 
generation to generation; but who does not know that it is certainly 
made up of particles in a state of swift transition ; the cataract is 
only a form resulting from the definite course which the changing 
particles pursue. The flame of a lamp presents to us for a long time 
the same appearance ; but its constancy of aspect is caused by a cease- 
less change in the place and condition of the chemical atoms which 
carry on combustion. Just so with man ; he appears an unchanged 
being endowed with permanent attributes of power and activity, but 
he is really only an unvarying form^ whose constituent particles are 
for ever changing. As the roar, spray, and mechanical power of the 
falling water are due to changes among the aqueous particles; 
and the heat and light of the flame are due to changes among com- 
bustible atoms ; so man's endowments of bodily activity, susceptibility, 
and force, originate in atomic transformations taking place iu his 



BASIS OF THE DEMAND FOR ALIMENT. 327 

Bystem. As each part is brought into action, its particles perish and 
are replaced by others ; and thus destruction and renovation in the 
vital economy are indissolubly connected, and proceed together. It is 
said, with reference to the casualties to which man is every where 
exposed, that "in the midst of life we are in death,'' but physiologi- 
cally, this is a still profounder truth ; we begin to die as soon as we 
begin to live. 

624. Rate at which the vital changes proceed. — But very few persons 
have any correct conception of the rate at which change goes on in 
their bodies. The average amount cf matter taken into the system 
daily, under given circumstances, has been determined with a con- 
siderable degree of precision. From the army and navy diet-scales of 
France and England, which of course are based upon the recognized 
necessities of large numbers of men in active life, it is found that 
about 2| lbs. avoirdupois of dry food per xlay are required for each 
individual ; of this about three-quarters are vegetable and the rest 
animal. Assuming a standard of 140 lbs. as the weight of the body, 
the amount of oxygen consumed daily is nearly 2^ lbs., which results 
from breathing about 25 or 80 hogsheads of air ; the quantity of 
water is nearly 4yL lbs. for the same time. The weight of the entire 
blood of a full-grown man varies from 20 to 30 pounds; of this, the 
lungs, in a state of health, contain about half a pound. The heart 
beats, on an average, 60 or 70 times in a minute. Every beat sends 
forward two ounces of the fluid. It rushes on, at the rate of 150 ft. 
in a minute, the whole blood passing through the lungs every two 
minutes and a half, or twenty times in an hour. In periods of great 
exertion the rapidity with which the blood flows is much increased, 
BO that the whole of it sometimes circulates in less than a single 
minute. — (Johnston.) According to these data, all the blood in the 
body, travels through the circulatory route 600 or 700 times in a day, 
or a total movement through the heart of 10,000 or 12,000 lbs. of 
blood in 24 hours. To assist in carrying forward the several bodily 
changes, various juices are poured out each day, according to the latest 
estimates, as follows : gastric juice, 14 to 16 lbs. ; bile, 3 to 4 lbs. ; pan- 
creatic juice, ^ lb. ; intestinal juice, ^ lb. — (Dr. Chambeks.) At the 
same time there escapes from the lungs nearly 2 lbs. of carionic acid 
and li of. watery vapor. The slcin loses by perspiration 2| lbs. of water, 
and there escape in other directions about 2|- lbs. of matter. In the 
course of a year, the amount of solid food consumed is upwards of 800 
-bs.; the quantity of oxygen is about the same, and that of water taken 
in various furms, is estimated at 1,500 lbs., or all togctlier a ton and a 



328 PHYSIOLOGICAL EFFECTS OF FOOD. 

half of matter, solid, liquid, and gaseous, is ingested annually. We 
thus see that the adult, of a half a century, has shifted the substance 
of his corporeal being more than a thousand times. 

625. A striking illnstration of these changes. — Let us take a signal 
example, which, although not falling within tlie limits of ordinary ex- 
perience, yet actually occurred in the course of nature. Thomas Parr, 
of England, lived to the age of 152 years. If we take the twelve 
years of his childhood, and double them over upon the succeeding 
twelve years of his youth, we shall have 140 years of adult life, or 
twice the common allotment of man. Applying to his case then the 
established physiological constants, we get the following startling 
results of the amount of possible change in matter produced in the 
lifetime of a single man. He drank upwards of a hundred tons of 
water, ate nearly sixty tons of solid food, and absorbed from the air 
one hundred and twelve thousand lbs. of oxygen gas to act upon that 
food. There ai"e fifteen lbs. weight of air resting upon every square 
inch of the earth's surface ; of this one-fifth is oxygen, there being 
therefore 3 lbs. of oxygen over every square inch of the earth, extending 
to the top of the atmosphere. The daily consumption by respiration 
is 2 lbs. Parr, therefore, consmned all the oxygen over a surface of 
236 square feet of ground to the very summit of the earth's atmos- 
phere, and generated noxious gases enough to contaminate and render 
unfit for breathing ten times that space, or poison a column of air 45 
miles high, having a base of nearly 2,400 square feet. If we may 
indulge in a somewhat violent supposition that the whole blood which 
was actually driven through his heart during that long period could 
have been accumulated and measured as one mass, by forming a pro- 
cession of vehicles, each taking a ton and occupying two rods of space, 
such a procession would have attained the enormous length of 2,000 
miles. 

626. Relation between Waste and Supply. — Such is the ground of our 
daily requirement for food. The annual supply of 3,000 lbs. of mattex 
to the body is demanded, because in the yearly exercise of its powers 
and functions 3,000 lbs. of matter have been used up or spent. It 
cannot be maintained for a moment that the bodily system possesses 
any power of producing or creating a single particle of the matter 
which it uses ; it must receive every thing from without, and maintain 
its uniform condition of weight by striking an exact balance between 
waste and supply, receipt and expenditure. There are two periods in 
the natural life of man when the balance between these antagonizing 
forces is overturned ; in infancy^ childhood and youth, the reception 



BASIS OF THE DEM^VND FOR ALIMENT. 329 

of matter prevails over its loss, and the body steadily augments iu 
weight ; in old age rei^aration does not keep pace with decay, and the 
bodily weight gradually declines. In the intervening period of adult 
life these antagonizing foi'ces are maintained with but little variation 
in a state of constant equilibrium. In all the deepest recesses of the 
body, in every springing muscle, and conducting nerve and connecting 
tissue, and even the thinking brain, myriads of atoms are continually 
passing into the condition of death, while by the profoundest law of 
physiological life an exactly equal number are constantly introduced 
to replace them, each of its proper kind and in its appropriate place. 

626. Practical inference from these factSt — As thus the living being is 
the result and representative of change on a prodigious scale, the 
question of the course, rate, and regulation of those changes must be 
controlling and fundamental. Matter is introduced into the system in 
one condition and escapes from it in another ; the change {metamor- 
phosis) that it has undergone is oxidation, or a true burning. The 
solid aliment is all combustible, oxygen is the agent which burns or 
destroys the food by uniting with it, and water the medium which 
brings them into proper relation to act on one another. Hence the 
life, activity, and multiform endowments of the organism, originate 
in the chemical action and reaction of prepared matter, borrowed 
temporarily from the outward world to be quickly restored to it again. 
And as the supply of nutritive matter is effected through our own 
voluntary agency ; as we select, mingle and prepare the nutritive mate- 
rials, and control the times, frequency, quantity and condition in which 
they shall be taken, and influence their physiological results in num- 
berless ways, it is clear that our practice, whatever it may be, must 
exert a direct and powerful influence upon the whole being ; its states 
of feeling, conditions of action, health, and disease. It is desirable 
therefore to gain the fullest possible understanding of the subject. 

627. Beneficent nse of Hnnger and Tliirst. — It will be seen from the 
nature of the case, that the necessities of the system for matter from 
without, are pressing and momentous. If the inflowing tide of gases 
be arrested but for a few moments, suffocation and death follow. If 
the liquid and solid aliments be withheld, indescribable agonies shortly 
ensue, and in a few days the extinction of life. There is, therefore, 
an irresistible life-demand for the supply of nutriment which cannot 
be put off upon peril of existence, while the cost of nutritive matter 
is laborious struggle and exertion, both of body and mind. Now it is 
plain, that if in the plan of our being the bodily requirement for food 
were left to the determination of reason, the purposes of nature would 



330 PHYSIOLOGICAL KFFECTS OF FOOD. 

be liable to continual defeat from indolence, carelessness or urgency 
of occupations. The Divine Architect has therefore wisely intrenched 
in the system two monitors, hunger and thirst, which are independent 
of reason or wiU, cannot be dislodged while life lasts, and whose duty 
it is to proclaim that further nourishment is required for bodily sup- 
port. And beside the sensations of hunger and thirst, imperative as 
they are, there is attached to their proper indulgence a degree of 
pleasure which never fails to insure attention to their demands. In 
what hunger and thirst consist, what state of the stomach or vessels 
produces them, or how the general nutritive wants of the sys- 
tem get expressed in feeling or sensation, we do not know ; several 
explanations have been offered upon this point, but they are all un- 
satisfactory. 

628. Impelled by the demands of the constitution food is procured, 
and in several ways, which have been described, prepared for use. 
When taken into the system it is subject to vai'ious changes in a cer- 
tain natural and successive oi'der, which wiU next be noticed. 

2. First Stage of Digestion — Ohanges of Food in the Mouth. 

629. The great olyect of Digestion. — The prepared food upon our tables 
is in the form of crude, unmixed, and chiefly solid masses. Various 
vegetables, breads, meats, butter, each with its peculiar constituents 
and properties, are ready for use. Their physiological purpose is to 
make blood, the source upon which the whole system draws for what- 
ever it requires. The blood contains every thing necessary to form all 
the parts, and produce all the peculiar liquids or secretions of the 
body. It circulates rapidly through every portion of the system, 
bearing all the constituents that can be required, while each part is 
endowed with the special power of withdrawing from the current as 
it passes along, just those particular constituents that it may require ; 
compounds of lime for bones and teeth, sulphurized compounds for the 
muscles, and phosphorized for the nerves, while various parts separate 
the liquids of secretion — the glands of the mouth attracting out the 
substances necessary to form saliva, those of the eyes the elements of 
tears, the coats of the stomach, gastric juice, and the liver, bile. The 
blood is a magazine of materials comprehensive enough for every want 
of the body, and all brought to a perfectly fluid condition, so as to 
flow with facility through the minutest vessels. Now, it is obvious 
that the food before us must bo profoundly changed before it can be- 
come blood. No one element of diet contains all the necessary ma- 



DIGESTION CHANGES IN THE MOUTH. 



331 



terials for this purpose ; the various articles must, therefore, be mixed. 
Some of the elements of food are incapable of forming blood ; these 
require to be separated, and the entire nutritive portion brought into 
a state of perfect liquidity. To effect these important changes in food 
is the great purpose of digestion^ which presents itself to our conside- 
ration in three distinct stages, commencing with transformations pro- 
duced in the mouth. 

C30. Redacing Mechanism of the Month. — The food, liquefied or soft 
ened, or with its texture relaxed, loosened, or made spongy by culi- 
nary methods, is reduced to small pieces by table instruments, and 
thus transferred to the mouth. An ingenious cutting and grinding 
mechanism here awaits it, to complete the mechanical operation of 
crushing and reducing. It consists of a double system of teeth, 
planted firmly in the jaws, and made to woi'k against each other by a 
set of powerful muscles. The 
teeth are so shaped and placed ^^' 

as to combine cutting, crushing 
and grinding, through vertical 
and side movements of the low- 
er jaw. The teeth are 82 in 
number, and their differences 
are illustrated by Fig. 113, which 
represents half the lower jaw. 
A shows two of the front or 
cutting teeth, called incisors; 
B the cuspid, canine, or dog tooth, so called from being large in the 
dog and carnivorous animals, and used by them to seize and tear their 
food ; G the licuspids or double-speared, from their resemblance to a 
double-headed canine tooth ; and D the molars, double-rooted, with 
broad, irregular, grinding surfaces.* 

631. Conditions of the flow of Saliva. — But no amount of mechani- 
cal action alone will convert solid aliment into the fluid state. If tho 
food is to be dissolved, there must be a solvent or liquid to bring about 
the solution. It is the office of the saliva or spittle to commence this 
work. The saliva is separated from the blood and poured into tho 
mouth by three pairs of glands (Fig. 114). The rate at which it is 
secreted vai'ies at different times and under different circumstances. 
The sight, or even the thought of dinner may fill the mouth with it, 
while continued mental attention to other subjects, or a state of anxi- 

*" In Latin, cuspi-it signifies the point of a spear ; canis, dog ; mola, a mill ; incisor 
anything which cuts." 




Illustration of the different liinds of Teeth. 



332 



PHYSIOLOGICAL EFFECT3 OF FOOD, 



Fig. 114. 




ety, will dry it up. The movements of the mouth, as in speaking, 
reading, or singing, excite its flow, but it is most copiously furnished 
at thnes of eating, by the contact and pressure of food during masti- 
cation. Ilence, the glands on that side of the mouth which is most 

used in mastication, secrete more than 
the others. The nature of the food 
causes the quantity furnished at meals 
to vary exceedingly ; hard, dry ali- 
ments provoking a much greater dis- 
charge than those which are moist 
and soft. It streams out abundantly 
f.a under the stimulation of spices, and 
continues to flow after the meal is 
concluded ; the secretion also goes on 
during sleep. 

632. Properties. — The saliva is a 
clear, slightly bluish, glairy juice, 
readily frothing. It contains less 
than one per cent, of saline matter, 
and in health is always alkaline. It 
Salivary glands; a parotid, J submaxil- contains also an organic principle 
lary, c sublingual. named ptyalln, an albuminous sub- 

stance which acts as a strong ferment. The tartar which collects 
on the teeth is the residue left by evaporation of the water of the sa- 
liva, and consists of earthy salts, cemented together by animal matter. 
The salivary juice of the mouth is, however, a mixture of three differ- 
ent salivas poured out by three pairs of glands. Pai'otid saliva is thin 
and watery, so as to be readily incorporated with the food by the 
teeth ; it also contains much lime. Submaxillary saliva is so thick 
and glutinous that it may be readily drawn out into threads. It is 
supposed to facilitate swallowing by affording a sort of anti-friction 
coating to the masticated food. The sublingual saliva is more limpid, 
resembling the parotid. 

633. Lses of Saliva. — Saliva serves not only to moisten and lubri- 
cate the mouth, and wet the aliment, so that it may assume a pasty or 
pulpy condition, but it is an indispensable medium for the sense of 
taste, as every thing is tasteless which the saliva cannot dissolve. By 
its frothy quality it embroils globules of air, and thus serves to convey 
oxygen into the stomach, where it probably plays a part in promoting 
the transformations. But beyond these important eftects, the saliva 
actually begins the operation of digestion in the mouth. If a little 



DIGESTION CHANGES IN THE MOUTH. 333 

pure starch be chewed for a short time, it will become sweet ; a por- 
tion of it has undergone a chemical transformation, and been con- 
verted into sugar. Bj its joint alkaline and fermentative powers, 
saliva produces an almost instantaneous effect upon starch, changing 
it first into sugar, and in a little longer time converting the sugar into 
lactic acid. This important change seems to be effected, not by any 
one of the salivary secretions, but is due to their combined action. 
Saliva exerts no solvent influence upon the nitrogenous aliments. It 
will thus be noticed that the first chemical attack, at the very thresh- 
old of the digestive passage, is made upon that alimentary principle 
which abounds most of all in our food (382). We furthermore draw a 
practical inference opposed to the current opinion which assumes that 
animal food, from its tough, fibrous nature, needs more mastication 
than vegetable. Meat and albuminous substances require to l.e thor- 
oughly disunited and subdivided in order that each particle may be 
brought into contact with the secreting membrane of the stomach, 
while bread, and substances which abound in starch, have not only to 
be reduced fine, but to be well imbued with the salivary liquid. In 
animal food, it is possible to supply the place of mastication by the use 
of implements in the kitchen and at the table ; but culinary science 
cannot compound an artificial saliva to be mixed with starchy food, so 
as to save the trouble of chewing it. The changing of this substance 
from a solid to a liquid form, as in gruel and sago slops, so that they 
are swallowed without being delayed in the mouth and mingled with 
its secretions, is unfavorable to digestion, especially if the stomach be 
not vigorous. The best condition in which starch can be taken is 
where the outer membrane has been ruptured by heat, and the mass 
made light, as in well-baked bread and mealy potatoes (532). 

634. Importance of thorough Mastication. — The mechanism of insali- 
vation has been inserted in the mouth for a definite and important 
purpose, and as the act of mastication is under the control of the will, 
it is very easy to defeat that purpose. If the food be imperfectly 
chewed, and hastily swallowed, or as the phrase goes, ' bolted,' the 
aliment passes into the stomach crude and ill-prepared, and the whole 
digestive function is just so far imperfect and enfeebled. It is of much 
consequence that meals should not be precipitated, but that proper 
time should be allowed to perform that portion of the digestive oi)era- 
tion, which falls so directly under voluntary control. Besides thought- 
lessness, and business pressure which pleads want of time, there is an- 
other cause of inattention to this matter which deserves notice. Many 
persons have placed themselves in such a falee relation to nature, as 



334 PHYSIOLOGICAL EFFECTS OF FOOD. 

to imagine that they exalt the spiritual attributes of their being by 
co&img contempt upon the pliysical. Such are inclined to regard the 
act of eating as a very animal and materializing operation, and any 
considerations of the way it should bo conducted, are apt to weigh 
but lightly upon their minds. This view is false, and leads to conse- 
quences practically mischievous. Dr. Combe remarks, — " Due mastica- 
tion being thus essential to healthy digestion, the Creator, as if to insure 
its being adequately performed, has kindly so arranged that the very 
act of mastication should lead to the gratification of taste — the mouth 
being the seat of that sensation. That this gratification of taste was 
intended, becomes obvious when we reflect that even in eating, nature 
makes it our interest to give attention to the process in whica we are 
for the time engaged. It is well known, for example, that when food 
is presented to a hungry man, Avhose mind is concentrated on the in- 
dulgence of his appetite, tlie saliva begins to flow unbidden, and what 
he eats is consumed with a peculiar relish. Whereas, if food be pre- 
sented to an individual who has fasted equally long, but Avhose soul ia 
absorbed in some great undertaking or deep emotion, it will be swallow- 
ed almost without mastication, and without suflBcient admixture with 
the saliva — now deficient in quantity — and consequently lie on the 
stomach for hours unchanged. A certain degree of attention to taste 
and the pleasures of appetite is, therefore, both reasonable and bene- 
ficial; and it is only when these are dbmed that we oppose the inten- 
tion of nature." 

635. EflFect of profuse Spittiug. — The salivary juices are parts of a 
great water circulation of secretion and absorption. They are poured 
into the mouth, not to le cast out, but to do a specific work, and then 
pass into the stomach and be again absorbed. If they are habitually 
ejected by spitting, the object of nature is contravened, and the sys- 
tem drained of that which it was not intended to lose. In such case 
the order of bodily functions is reversed, and the mouth is converted 
into an organ of excretion. It is the ofiice of the kidneys and urinary 
ducts to convey away a large part of the superfluous water, and aU 
the waste salts that require to be expelled from the body ; but if a 
drain be established at the mouth, the eftect is to relieve those parts 
of a portion of their labor. " When the inipm-e habit of profuse spit- 
ting is indulged in, it is interesting to remark the reflected effect which 
takes place in the reduced quantity of the urinal excretion, and an in- 
stinctive desire for water, a kind of perpetual thirst. It is probable 
that, under these disgusting circumstances, the percentage amount of 
saline substances in the saliva is increased, and that, so far as that 



WOESTK'N — CHANGES IN THE STOBIACH. 



335 




Section of the human stomach : a esophagus ; & c cardiac 
orifice ; d e greater curvature ; / ff lesser curvature ; fi 



class of bodies i; cone orned, the salivary glands act vicariousb ior the 
kidneys, and the luimth is thus partially converted into t urinary 
aqueduc ." - -(Tir Tn .pee.) 

3. Second Stage of Digestion— Change of Food est the {tomaoh. 

636. Figure and Dimensions of the Organ.— Having underf, )Qe moro 
or less perfectly the changes which appertain to the mouth, the food 
is swallowed, and pass- Fio. 115. 

ing down the esopha- 
gus, or gullet, enters 
the stomach. This or- 
gan is a pouch-shaped 
enlargement of the di- 
gestive tube, having 
the form shown in Fig. 
115. The larger ex- 
tremity is situated at 
the right side of the 
body, and its lesser end 
at the left. That por- 
tion where the esoph- P^l""*' ""'^^'^ ' ^^ duodenum ; k bile duct, 
agus enters it, is termed the cardiac region (because it is in the vicin- 
ity of the }:ear or heart) ; the other extremity, where the contents of 
the stomach escape into the intestine, is known as the pyloric region 
(from pylorus, a gate-keeper). The capacity of the human stomach 
of course varies considerably, but on an average, it will hold when 
moderately distended about three pints. As a general rule, it is larger 
among those who live upon coarse, bulky diet. In different animals 
the size of the stomach varies exceedingly, according to the concen- 
tration of the food upon which they live. Thus in the flesh-eating 
animals it is very small, only a slight enlargement of the esophagal 
tube ; while in those which feed upon herbage, it is distended intc 
an enormous cavity, or rather into several, as in the ruminants, cows, 
sheep, &c. 

637. Layers of the Stomacb. — The walls of the stomach consist of 
three membranous coats. The outer layer is a smooth, glistening, 
whitish membrane {serous memirane), lining the abdomen, and cover 
ing all the internal organs, which it strengthens, and by its smoothness 
and constant moisture, permits them to move upon each other with- 
out irritation. The middle coat consists of two layers of muscular 
fibres or bands, one of which runs lengthways, and the other crosswaya. 



336 PHYSIOLOGICAL EFFECTS OF FOOD. 

or around the organ. By means of tlicse muscles t". o stomach may 
contract its dimensions in all directions, so as to adapt its capacity to 
the amount of its contents. They also give to the organ its constant 
motion during digestion. The third layer of the stomach (mucous mem- 
brane) lines its internol surface. It is a soft, velvet-like membrane, 
of a pale pink color, in health, and of much greater extent than the 
outer coats, by which it is thrown into folds or wrinkles. It is con- 
stantly covered with a thin, transparent, viscid mucus. 

638. Motions of the Stomach. — The food upon which operations have 
been commenced in the mouth, is passed into the stomach, but it is 
not permitted to rest. By the successive contraction and relaxation of 
its muscular bands, the stomach imparts to its contents a constant 
churning, or revolving motion. In the celebrated case of St. 
Maktix, a Canadian soldier, whose stomach was opened by a gunshot 
wound in the side, and healed up leaving a permanent orifice (gastric 
fistula), Dr. Beaumont made numerous observations of digestive 
phenomena. He thus describes the movements of food within the or- 
gan. " After passing the esophagal ring it moves from right to left along 
the small arch ; then tlirough the large curvature from left to right. The 
bolus (swalloicecl mouthful), as it enters the cardiac, turns to the left, 
descends into the splenic extremity (large extremity near the spleen)^ 
and follows the great curvature towards the pyloric end. It then re- 
turns in the course of the smaller curvature, performing similar revolu- 
tions. These revolutions are completed in from one to three minutes. 
They are slower at first, than after digestion is considerably ad- 
vanced." The motion is not absolutely constant, but continues for a 
few minutes at a time. If the food remains in the stomach three 
hours it travels round and round through this circuit two or three 
hundred times: — to what purpose? 

639. Miaate arrangements for Stomach Digestion. — Before considering 
what takes place in the stomach, we must have a closer view of its 

mechanism. The lining layer of this organ is curi- 

^1^ ously and admirably constructed, though it requires 

^^.^wR^^ the microscope to see it. Magnified about 70 

^B^Bnaj^m diameters the mucous membrane exhibits the honey- 

mSS^^K^^^ combed appearance seen in Fig. 116. Into these 

■^^^^^— '•^ reticulated spaces, there open little cup-shaped 

cavities called stomach follicles, which are about 

,.^^/-. 1"2Q0 of an inch in diameter. They are closely 

packed together in the mucous membrane, so that 

when it is cut through, and view'ed with the microscope, it looks 



DIGESTION CHANGES IN THE STOMACH. 



337 



Fia. 117. 




like palisading, or like little flasks or test-tubes close packed and up- 
right ; many thousands of these upright cylindrical cavities being 
eet in a square inch of surface. They are of different depths in 
different parts of the stomach, and they terminate at the bottom in 
minute closed tubes. The arrangement has been 
likened to a little glove, the hand of which opens 
into the stomach, while the fingers are buried in 
the tissue beneath. Fig. 117, represents the se- 
creting follicles in the stomach of a dog after 
twelve hours' abstinence ; «, from the middle re- 
gion of the stomach ; I, from near the pylorus ; c d, 
the mouths opening upon the surface, e f^ the closed 
tubes imbedded in the membrane below. The walls 
of these cavities are webbed over with a tissue of 
most delicate bloodvessels, carrying streams of blood 
— a network of veins surrounds their outlets upon 
the surface of the membrane, while nerves innu- e] 
merable pervade the whole an-angement. 

640. Use of these little poeket-sUaped vessels. — What, now, is the 
purpose served by these interesting little contrivances ? It is to 
separate from the blood the digestive fluid of the stomach. But they 
do not effect this directly ; another agency, — that of cells (49G), — is 
called into play. The gastric juice does not simply ooze or distil 
from the blood into the stomach. It is manufactured by a determi- 
nate process. " For each minutest microscopic drop of it, a cell of 
complex structure must be developed, grow, burst and be dissolved." 
At the bottom of the cavities, in the little tubular roots, the seeds or 
germs of cells arise in immense numbers. Eecurring to the simile of 
the glove, within each finger, at the tip and upon its sides, the cells 
take origin, and, nourished by the blood, multiply and swell until 
they are driven up in crowds into the hand or larger cavity, and hav- 
ing reached their full maturity, are pushed out at the surface, burst, 
and deliver their contents into the stomach. 

641. The periodic supply of Food. — The digestive principles are thug 
a product of cell-action, and into their preparation there enters the 
element of time. Though short-lived, a certain period must elapse 
for their production. During digestion the cells are perfected in in- 
credible numbers, and yield large amounts of fluid. During fasting, 
no full-grown cells escape ; the tubes collapse, and an opportunity is 
allowed for the production of a new stock of germs or cell-grains. If 
this be so, it must follow that we cannot with impunity interfere with 

15 



333 PHYSIOLOGICAL EFFECTS OF FOOD. 

tbat which seems a natural rule, of allowing certain intervals between 
the several times of eating. Every act of digestion involves the con 
sumption of some of these cells ; on every contact of food some must 
quickly perfect themselves, and yield up their contents ; and without 
doubt, the design of that periodical taking of food, which is natural to 
our race, is, that in the intervals, there may be time for the production 
of the cells that are to be consumed in the next succeeding acts of di- 
gestion. We can, indeed, state no constant rule as to the time re- 
quired for such constructions ; it probably varies according to age, the 
kind of food, the general activity or indolence of life, and above all, ac- 
cording to habit ; but it may be certainly held, that when the times 
are set, they cannot with impunity be often interfered with ; and as 
certainly, that continual or irregular eating is wholly contrary to the 
economy of the human stomach. — (Paget.) '' 

648. Properties of Gsistric Juice. — The digestive juice of the stomach 
is a colorless, inodorous, slightly viscid fluid, which when removed 
from the organ, retains its active properties for a long time, if kept 
excluded from the air. A boiling heat destroys its activity, but freez- 
ing does not. In a healthy state, it is always distinctly sour, which is 
caused by an uncombined acid, usually the hydrochloric, but some- 
times lactic acid. "With its acid principle, the gastric juice also con- 
tains a peculiar albuminous body called ' pepsin ' or 'ferment sub- 
stance.' If the juice be evaporated to dryness, this pepsin constitutes 
three-fourths of the solid residue. As the food is rolled round in the 
stomach, it is incorporated with this juice, and changes gradually to 
a pulpy semi-fluid mass. Digestion is fully under way in an hour 
after the meal is taken, and is usually finished in about four. 

644. Limit of Stomach Digestion. — Eecent physiological investigations 
have exploded the opinion long entertained, that the stomach is the 
exclusive or principal seat of digestive changes. In tracing the 
properties of foods, we had occasion to divide them into two great 
classes based upon fundamental difierences in chemical composition — 
the nitrogenous and the non-nitrogenous aliments. We find this dis- 
tinction recognized by nature in arranging her plan of digestion. So 
diiferent are these two kinds of aliments that they require totally 
different agents to dissolve them, — nay, solvent fluids of entirely 
opposite characters. We have seen that digestion began in the mouth 
with an alkaline liquid, and took effect only upon the non-nitrogenous 
principles. Upon proceeding to the stomach we find new conditions — 
an acid liquid replaces the alkaline — the changes that commenced in 
the mouth are partially or totally suspended, the non-nitrogenous com- 



DIGESTION CHANGES IN THE STOMACH. 339 

pounds remain unaltered, tlie gastric fluid taking eflfect only upon 
nitrogenous substances. 

645. iction of the Acid and Ferment. — If coagulated white of egg 
be placed in water acidulated with hydrochloric acid, no solvent 
action takes place at common temperatures for a long time. If the 
temperature be raised to 150°, a slow dissolving effect begins, which 
is much increased at the boihng heat. But if a little ' pepsin ' be 
added to the liquid the solution goes on actively, so that the pepsin, 
as it were, replaces the eflfect of a high temperature. An ounce of 
water mixed with twelve drops of hydrochloric acid and one grain 
of pepsin, wiU completely dissolve the white of an egg in two hours 
at the temperature of the stomach (100°). It acts in the same manner 
on cheese, flesh, vegetable gluten, and the whole nitrogenous group, 
changing them to the liquid form. These are the results of an arti- 
ficial gastric juice, but they are exactly the same in hind as those 
which take place in the stomach. Drs. Bidder and Schmidt, whose 
researches upon digestion are the most recent and extensive, have 
shown that gastric juice withdrawn from the stomach and placed in 
vials, produces upon food precisely the same alterations as occur in 
the stomach, only much more slowly. In consequence of the motions 
of the stomach turning the aliment round and round, and the flow of 
the secretions which constantly washes away the dissolved parts and 
exposes fresh surfaces, the action proceeds about five times faster 
within the body than without, but the nature of the results is iden- 
tical. 

646. What is the Digestive Ferment Substance ? — There has been much 
controversy about pepsin ; what is it ? A substance in the gastric 
fluid discovered by ScnwAN a few years ago, and supposed to be a 
peculiar principle specially prepared for digestive purposes. It may 
be obtained from gastric juice, or by soaking the membrane of a calf's 
stomach (rennet). "When proper means are taken to separate and dry 
it, it appears as a yellow gummy mass. Its potency for digestive pur- 
poses was proved by Wasmann, who showed that a solution containing 
only l-60,000th part, if slightly acidulated, dissolves coagulated albumen 
in six or eight hours. Liebig is, however, disinclined to regard pepsin 
as a peculiar digestive agent. He maintains that the fermentative 
change of digestion is due to minute parts of the mucous membrane of 
the stomach, separated and in a state of decomposition. The surface of 
that membrane is lined with what is called epithelium^ composed of 
exceedingly thin filmy cells ; and physiologists have discovered, that 
during digestion it separates completely from the other layers of the 



340 PHYSIOLOGICAL EFFECTS OF FOOD. 

membrane. This epithelium, acted on by the oxygen swallowed in 
the frothy saliva, excites the digestive fermentation attributed to 
pepsin. It may be remarked that this stomach fermentation cannot 
change the starch of food into alcohol and carbonic acid, nor give rise 
to gases, although in morbid conditions of the organ other fermenta- 
tions may arise in the alimentary mass. 

647. Gastric Digestion something more than Solution. — It was formerly 
thought that digestion was simply solution, or change of alimentary 
matter to the liquid state ; but late investigations inform us that nu- 
tritive substances are more than dissolved, they are really altered in 
properties. The nitrogenous matters are not only dissolved, but are 
so modified as to remain dissolved. In ordinary solution a solid body 
is changed to a liquid by the action of another liquid or solvent ; but 
when the solvent is removed the dissolved substance again resumes its 
solid condition. Not so, however, in gastric digestion ; the digestive 
fluid dissolves albumen, fibrin, casein ; but as it cannot accompany them 
to maintain them in this state, it impresses upon them a still further 
change, by which they continue soluble. Casein in milk, and liquid 
albumen are already dissolved when swallowed ; but they are not 
digested, and the first act of the stomach is to coagulate or solidify 
both. They are then dissolved again, and so altered as to retain the new 
condition under circumstances which would have been before impos- 
sible ; while their capability of being absorbed, so as to pass into the 
blood, is greatly increased. The term '•peptone ' has been given to 
nitrogenous matters changed in this way ; thus albumen produces 
an albumen-peptone ; fibrin, a fibrin-peptone ; and casein, a casein- 
peptone, — substances which have lost the power of coagulating or 
setting into a jelly as they did when dissolved before. It has been 
found that oil plays a part in the changes by which the peptones are 
produced ; so that, although oily matters are certainly not themselves 
digested in the stomach, they are made to serve a useful purpose in 
passing through it. The nitrogenous matters are not chemically 
altered, except perhaps by combining with water, 

648. Action of Saliva in the Stomach. — The alkaline saliva attacks 
the sugar and starch in the mouth, and has the power of rapidly 
changing the starch into sugar, and that into lactic acid. But the 
food tarries only a few moments in the mouth ; charged with its alka- 
line solvent, it descends into the acid region of the stomach. But 
acids and alkalies cannot get on together. They either kill each 
other, or if one is the strongest or most abundant, it destroys the 
other though not without injury to itself. Hence, whenever the saliva 



DIGESTIOK — CHANGES EN THE STOMACH. 341 

and gastric jnice come into contact, the former will be neutralized by 
the excess of the latter, and a stop put to its action. Yet this does 
not occur instantaneously, as the food is swallowed. The eiFect of the 
gastric juice is superficial, acting at nrst upon the food where it comes 
in contact with the bedewed coats of the stomach, while the saliva, in- 
corporated within, is allowed a little time for- action. In this limited 
sense there may be two digestions going on in the stomach, although 
gastric digestion speedily overpowers and suspends the salivary. It 
is interesting to remark that lactic acid may replace hydrochloric in 
stomach digestion, and that if from any cause the latter is not supplied 
in due quantity, the saliva, acting upon the contents of the stomach, 
will generate the required substitute. 

649. Qnautity of Gastric Jnice secreted. — There has been, and indeed 
there still is, niuch doubt upon this point ; but it is now generally con- 
ceded that former estimates ranged much too low. The hourly de- 
struction of fibrin throughout the system, in average muscular action, 
has been assumed at 62 grains, and it has been found that 20 
parts of gastric juice are needed to dissolve one part of dry nitro- 
genous matter. To digest this quantity only, some 60 or 70 ounces 
of the fluid would be required. It is obvious that the natural quanti- 
ty must much exceed this, as a considerable portion will be neuti'alized 
by the saliva, and much inevitably escapes into the intestines. But 
observation indicates quantities greatly higher than any calculated re- 
sults. In the case of dogs, Bidder and Schmidt found from experi- 
ment the proportion to be one-tenth of their weight. This proportion 
applied to man would give a daily secretion of 14 lbs. Dr. Geune- 
WALDT has however quite recently had an opportunity of determining 
the quantity yielded by the human body, in the case of a stout, healthy 
peasant girl, weighing 120 lbs., who had a fistulous opening in her 
stomach, from childhood, that did not in the least degree interfere 
with her general health. His experiments gave the astonishing result 
of 31 lbs. of the gastric secretion in 24 hours, or one-fourth the weight 
of the body. Making every possible allowance for error in these in- 
vestigations, we must conclude that the quantity of digestive fluid 
poured out each day must, at any rate, be very large. 

650. Digestibility of Foods. — By this we understand their capability of 
yielding to the action of the digestive forces, the joint result of seve- 
ral distinct chemical agents fitted to act upon special constituents of 
the food, and brought into play throughout the whole alimentary 
tract. Digestion is therefore an aftair of many conditions, and its re- 
eults are by no means capable of being so simply stated as has been 



342 PHYSIOLOGICAL EFFECl'S OF FOOD. 

fonnerly believed. What goes forward in the stomachy although of 
great importance, atlords but a partial view of the whole operation. 
Dr. Beattmont made an admirable series of observations upon thia 
organ, and did much to advance the inquiry. Yet the value of hia 
observations was diminished by the imperfect knowledge of his time, 
for we see bim constantly misled by the conviction that there is but 
one digestive agent, the gastric juice, and but one digestion, that in 
the stomach. We speak of Ms time, as if he might have lived long ago. 
Measuring the time by the course of investigation, he did live long 
ago. The history of science has a chronology of deeds, and marks otf 
time by what has been accomplished. Dufay, announcing the first laws 
of electricity, in 1737, stood much nearer Thales, of ancient Greece, 
rubbing his piece of amber, than to Prof. Morse, patenting the electro- 
magnetic telegraph, in 1837. Within a quarter of a century, organic 
and animal chemistry have risen to the position of separate and in- 
dependent branches of science ; and it is hardly an exaggeration to say 
that more has been done to elucidate the subject of digestion in the 30 
years that have elapsed since Dr. Beaumont began his experiments, 
than was accomplished by all the physiologists who preceded him, 
though we are far enough yet from any thing like a clearing up of the 
subject. Eegarding digestion comprehensively, as the blood-forming 
function, we are to take into account not only the solubility of ali- 
ments, but their conformability to the blood. If two substances are 
dissolved with equal ease, that will be the more digestible which has 
the greatest similarity to some constituent of the blood. Gum, for 
example, is much more easily dissolved than fat, yet the latter is a 
constant constituent of blood, while the former is never found there. 
Gum, to be made available, must pass through a series of transforma- 
tions, — sugar, lactic acid, butyric acid, while fat passes into the circu- 
lation without decomposition. " If the conformity of two alimentary 
principles with the constituents of the blood is equal, the more soluble 
is the more digestible. Soluble albumen and fibrin stand equally near 
to the blood, both being contained in it ; as the soluble albumen is 
however more readily dissolved in the digestive juices than fibrin, the 
digestion of the latter is more difficult." We thus see that the diges- 
tibility of foods is not the mere matter of the time of solution in the 
stomach that has been generally supposed, but involves much more. 
Meanwhile, Dr. Beaumont's statements of the periods which various 
alimentary substances require to break down into chyme in the 
stomach, may be serviceable, if received with due restrictions. We 
Bubjoin an abstract. 



DIGESTION — CHANGES IN THE STOMACU. 



343 



MEAN TIMES OF CHTMIFICATION OF FOOD. 



Eice 

Pig's feet, soused... 

Tripe, soused 

Trout, salmon, fresh 

Apples, sweet, mellow 

Venison, steak 

Sago 

Apples, sour, mellow. 
Cabbage with vinegar 
Codfish,' cured, dry . . . 

Eggs, fresh 

Liver, beefs, fresh. . . . 

Milk 

Tapioca 

Milk 

Turkey, wild 

" domesticated 

Potatoes, Irish 

Parsnips 

Pig, sucking 

Meat hashed with ) 

vegetables ) 

Lamb, fresh 

Goose 

Cake, sponge 

Cabbage-head 

Beans, pod 

Custard 

Chicken, fnll-grown . . 

Apples, sour, hard 

Oysters, fresh 

Bass, striped, fresh . . . 
Beef, fresh, lean, rare 

" steak 

Corn cake 

Dumpling, apple 

Eggs, fresh 

Mutton, fresh 



Preparation. 


Time. 




h.m. 


Boiled 


1 — 


Boiled 


1 — 


Boiled 


1 — 


Boiled 


1 30 


Fried 


1 80 


Raw 


1 30 


Broiled . . . 


1 35 


Boiled 


1 45 


Kaw 


2 — 


Kaw 


2 — 


Boiled..... 


2 — 


Eaw 


2 — 


Broiled. . . . 


2 — 


Boiled .... 


2 — 


Boiled .... 


2 — 


Kaw 


2 15 


Koasted. .. 


2 18 


Boiled 


2 25 


Koasted . . . 


2 80 


Baked 


2 80 


Boiled 


2 30 


Koasted . . . 


2 30 


Warmed. . . 


2 80 


Broiled. . . . 


2 80 


Koasted.. . 


2 30 


Baked 


2 30 


Kaw 


2 80 


Boiled 


2 30 


Baked 


2 45 


Fricasseed. 


2 45 


Eaw ' 


2 50 


Raw 


2 55 


Broiled 


3 — 


Roasted . . . 


3 — 


Broiled 


3 — 


Baked 


3 — 


Boiled 


3 — 


Boiled soft. 


3 — 


Broiled. . . . 


3 — 


Boiled .... 


3 — 



Pork, recently salted. . 

Soup, chicken 

Oysters, fresh 

Pork, recently salted . 

Pork steak 

Corn bread 

Mutton, fresh 

Carrot, orange 

Sausage, fresh 

Beef, fresh, lean, dry. . 
Bread, wheat, fresh. . . 

Butter 

Cheese, old, 8trox.g. . . . 
Eggs, fresh 

Flounder, fresh 

Oysters, fresh 

Potatoes, Irish 

Soup, mutton 

" oyster 

Turnip, flat 

Beets 

Corn, green, & beans. . 

Beef, fresh, lean 

Fowls, domestic 

Veal, fresh 

Soup, beef, vegeta- ( 
bles, and bread 1 

Salmon, salted 

Heart, animal 

Beef, old, hard, salted 
Pork, recently salted. 
Cabbage, with vinegar 

Ducks, wild 

Pork, recently salted. 

Suet, mutton 

Veal, fresh 

Pork, fat and lean .... 

Suet, beef fresh 

Tendon 



Prcpariition. 


Time. 


Eaw 


h.m. 
8 — 


Boiled.... 


3 — 


Roasted... 


8 15 


Broiled.... 


3 15 


Broiled.... 


3 15 


Baked 


3 15 


Roasted... 


8 15 


Boiled .... 


8 15 


Broiled 


3 20 


Roasted . . . 


S >0 


Baked 


3 80 


Melted.... 


3 30 


Raw 


8 30 


Hard boil'd 


8 80 


Fried 


8 30 


Fried 


3 80 


Stewed . . . 


3 30 


Boiled .... 


8 30 


Boiled .... 


3 30 


Boiled .... 


3 80 


Boiled.... 


3 80 


Boiled.... 


3 45 


Boiled.... 


8 45 


Fried 


4 — 


Boiled .... 


4 — 


Roasted.. . 


4 — 


Broiled . . . 


4 — 


Boiled .... 


4 — 


Boiled .... 


4 — 


Fried 


4 — 


Boiled .... 


4 15 


Fried 


4 15 


Boiled .... 


4 30 


Roasted... 


4 30 


Boiled....' 


4 80 


Boiled .... 


4 80 


Fried 


4 30 


Roasted.. . 


5 15 


Boiled .... 


5 80 


Boiled .... 


5 80 



651. Absorption from the Stomach. — The power possessed by liquids 
and gases of penetrating and passing through membranes, is of the 
highest physiological importance ; indeed it is one of the primary 
conditions of life. The little cell, the starting-point of organization, 
is a closed bag — without an aperture. All its nourishment must 
therefore pass through its membranous wall. So also with the perfect 
animal body. Currents and tides of juices are constantly setting this 
way and that, through the membranous sides of vessels. The liquefied 
food is destined to pass into the blood, but there is no open door 
or passage by which it can get there, and so it enters the circu- 
lating vessels by striking at once tlirough their sides. In this way, 
water drank is absorbed by the minute veins distributed over the sur- 
face of the stomach, and enters the circulatory current dirot tly. This 



344 



PHYSIOLOGICAL EFFECTS OF FOOD. 



is proved by the fact that when the outlet to the stomach is closed hj 
tying the pyloric extremity, water which has been swallowed rapidly 
disappears from the organ, and medicines taken produce their eftecta 
upon the system almost as promptly as under natural circumstances. 
In the same way portions of sugar, lactic acid and digested nitro- 
genous substances, which are dissolved in water, pass into the blood 
by absorption through the stomach veins. The contents of the stomach 
thus leave it in two directions, — a portion is absorbed through the 
coats of the organ, while the unabsorbed matters gradually ooze 
through the valvular opening that leads into the intestine. 

4. TniKD STAGE OF DIGESTION — CHANGES OF FoOD IN TUB INTESTINES. 

652. Digestive Juices of the Intestinal Tube. — The partially digested 
food dismissed from the stomach enters the duodenum, the first por- 

FiG. lis. 



Large intestines 



Append ra of ,- 
cacum 




Spleen 



Small iiit«8tis«s 



Small IntcfitiDei 

Digestive tract in man. 



DIGESTION — CHANGES IN THE INTESTINES. 345 

tion of the intestinal tract (small intestine). This is a tube about 20 
feet in length, with a surface of some 3,500 square inches, and is the 
organ designed for finishing the digestive process. The general 
scheme of the digestive tract in man is exhibited in Fig. 118. Into 
the duodenum, and but a few inches from the valve of entrance, two 
small tubes (ducts) open, one leading from the liver and pouring in 
&iZi?, and the other from the pancreas, yielding pancreatic _;wic<3, the 
quantity of the former being much greater than of the latter. Both 
of these liquids are strongly alkaline from the presence of soda. The 
pancreatic juice much resembles saliva in properties; indeed the 
pancreas itself is so like the salivary glands as to be grouped with 
them. From the walls of the intestine there is also poured out a 
fluid called the intestinal juice. It is secreted in small but variable 
quantities, and is alkaline like the other secretions. 

653. Changes ia the Intestinal Passage. — We find that the alkaline 
digestion of the mouth is now resumed. The starch is attacked ener- 
getically and rapidly changed into sugar, and that to lactic acid. The 
oily substances hitherto untouched by the digestive agents are now 
acted upon, not perfectly dissolved like the other alimentary matter 
but reduced to the condition of an emulsion, its particles being verj 
finely divided and rendered capable of absorption. It is believed that 
the Pancreatic juice is the efficient or principal agent in producing 
these changes ; although the bile undoubtedly contributes to the effect 
in some way not yet understood. As undigested albuminous matter 
is constantly liable to escape through the pyloric gateway into the in- 
testines, it seems required that they should be capable, upon emer- 
gency, of completing the unfinished work, and such really appears to be 
the case. Although the secretions poured into the intestine are all 
distinctly alkaline, yet they convert sugar so actively into lactic acid, 
that the intestinal mass quickly becomes acidulous, — strongly so, as it 
advances to the lower portion. The conditions are thus afforded for 
the digestion of nitrogenous matters in the intestines, which is known 
often to take place, although their ordinary function is admitted to be 
digestion of non-nitrogenous substances, starch, sugar, and fat. 

654. Absorption from the Intestine. — The nutriment being finely dis- 
solved, is absorbed through the coats of the intestine, but not all in 
the same manner. Those substances which are completely dissolved 
in water, are taken up by the veins, which are profusely distributed 
over the intestinal surface, while the oily and fatty matters, which are 
not so perfectly dissolved, are taken up by a special arrangement of 
vessels, called the lacteals, which are extremely fine tubes arising in the 

15* 



346 PHTSIOLOGICAL EFFECTS OF FOOD. 

intestinal coats. They were formerly supposed to be open at their ex- 
tremities, but they are now seen to present fine, blunt ends to the in- 
testinal cavity. How oily substances get entrance into these tubes is 
an old physiological puzzle. The membrane is moist, and water repels 
oil ; how then can it be imbibed ? Yet it constantly flows through. 
Tlie thing is accomplished by the agency of cells, which are produced 
in vast numbers during lacteal absorption. These contain the oil, and 
bursting, deliver it to the absorbent vessels. The liquid which enters 
the iacteals is white, milk-like, and rich in oil. These veseels are 
gathered into knots (glands), so as to be greatly prolonged without 
consuming space. They finally gather into a tube (thoracic duct), and 
pour their contents into a large vein near the left shoulder. In its 
route, there is a disappearance of the large proportion of oil ; and 
albumen, which either entered from the intestine, or has afterwards 
transuded from the bloodvessels into the lacteals, is gradually 
changed to fibrin, the liquid acquiring the power of clotting or coag- 
ulating, 

655. Constipating and Laxative Foods. — The walls of the alimentary 
canal having absorbed from its contents such parts as are adapted for 
nourishment, there remains an undigested residue which passes at in- 
tervals from the bowels. The conditions of the intestines in reference 
to tlie retention or ready passage of excrementitious matters, is liable 
to variation from many causes. Amongst these, the nature of the 
food itself is influential. Some aliments have a relaxing eftect, and 
others are of a binding nature, or tend tp constipation, and they differ 
much in the degree in which these efffects are produced. These re- 
sults are not, however, always due to specific active effects produced 
upon the bowels ; for some foods, as meats, eggs, milk, are considered 
to be binding, because they are completely absorbed, and leave no 
residue to excite the intestines to action. Those aliments are best 
adapted to relieve a costive habit of body which leave much undigested 
refuse to stimulate the intestines to free action. In this relation wo 
may group the most important aliments, according to their reputed 
characters, as follows : 

THOSE OF A CONSTIPATING TENDENCY. THOSE OF A LAXATIVE TENDENCY. 

Bread and cakes, from fine wheaten "Wheaten bread and cakes from un- 

flour; rice, beans, peas, meats, eggs, tea, bolted flour, rye bread, corn bread, raw 
slcoholic drinks. sugar, (from the molasses it contains,) fruits, 

raw and cooked, and generally substancea 
abounding in ligneous matter,as skins, cores, 
husks, bran, &c. 



ITS FINAL DESTINATION. 347 



5. Final Destination of Foods. 

656. Digested alimentary matter enters the circulation and becomes 
BLOOD. This fluid is contained in a system of vessels, which extends 
to all parts of the body. It has been aptly called the floating capital 
of the system, lying between absorption and nutrition. Its quantity 
in an average-sized man is estimated at from 20 to 24 lbs. It is whirled 
as a rapid stream Incessantly through the body, circulating round and 
round, so as to be brought into relation with all parts (624). 

657. Composition of Blood. — The composition of blood varies slightly 
with age, sex, constitution, and state of health ; it is also liable to acci- 
dental variations, as the supplies to it are periodic and fluctuating, 
while the draught upon it, though constant, is unsteady. It consists 
of about 78 per cent, water and 22 per cent, solid food dissolved in it. 
"When evaporated to dryness, the solid matter is found to consist of: 

Fibrin Albumen Gelatin 93 per cent. 

Fat, a little sugar, and a trace of starch 2 " 

Saline matter, or ash 57 " 

Blood 100 " 

658. Blood Discs, Globules, or Cells. — To the naked eye blood appears 
of a red color, but under the microscope it is seen as a transparent, 
watery fluid, containing vast numbers of little floating cells or discs, 
which are the grand instruments of change in the sanguinary fluid. 
Their minuteness is amazing; fifty thousand would be required to 
cover the head of a small pin, while in a single drop of blood which 
would remain suspended upon the point of a fine needle, there must 
be as many as three millions. And yet each of these little bodies, 
which dwells down so low in the regions of tenuity that the unas- 
sisted eye cannot discover it, seems to be an ^ 

"^ ' Fig. 119. 

independent individual, which runs a definite 

career, is born, grows, performs its ofiices, and /^f\ °C 

dies like the most perfect being, though the phy- ^ ^^ O^**^ h 

Biologist tcUs us that twenty millions of them 

perish at every beat of the pulse. Figs. 119 anc^ 

120, from a work of Dr. Hassall, represent 

different aspects of the blood discs, as seen under ,^ ^ 

the microscope. The physiology of the blood \J 

in its details is curious and most interesting, but ^ 

we have no space to consider it here, and it is „ , ,, \, , ,_ , 

. ' Human red blood globtiies, 

not neccssaiy to the general view wo propose showing their natural form 
to give of the final influence of food upon the b?o!ight"iui'iy'i'nttf.)ciis?'*'" 
tywteiii. 





348 PHYSIOLOGICAL EFFECTS OF FOOD. 

659, Grand purpose of the Ilamaa Body. — The living man is pre* 
Bented to our consideration as an engine of power — a being capable of 
producing effects. The bony framework within is broken into numer- 
ous pieces to admit of free motion. A complicated and extensive ap- 
paratus of contractile muscles is provided for me- 
chanical movement. The nervous system binds 
the "whole into a co-operating unity, presided over 
by the brain, which not only regulates and gov- 
erns the animal nature, but is the material seat oi 
intellectual power. Altogether, the body dis- 
closes its supreme purpose to be the reception of 
impressions by the senses, and the development 
and expenditure of physical and mental force. 
But force cannot be produced out of nothing. 
The body cannot and does not create it. As there 

Blood discs seen united ig no evidence that in the course of events upon 

into rolls, like adlierent 

pieces of money. the earth, there is either the creation or destrac- 

tion of a single atom of matter, so it is believed 
that in no absolute sense is force either created or destroyed. It 
changes states, disappears, and remains latent or reappears in different 
forms, but its total amount is thought to correspond with the total 
quantity and fixed properties of matter. Power is thus not literally 
generated in the body, but is developed or made active there by cer- 
tain definite causes. It is desirable to understand, as far as we may 
be able, the conditions of its production. 

660. Food produced by the action of Forces. — The stream of aliment 
which flows into the sj^stem from without, consists mainly of carbon, 
oxygen, hydrogen, and nitrogen. These, when left to the undisturbed 
play of their attractions, take the compound form of water, carbonic 
acid, and ammonia, natural and permanent conditions of equiUbrium 
from which they are not inclined to depart. These three substances 
constitute the chief nourishment of the vegetable kingdom. Through 
the roots, or by direct absorption from the air, they get admission into 
the vegetable leaf, the crucible of nature, where organized compounds 
originate. They are there decomposed and thrown into new arrange- 
ments, forming new compounds. Simple substances, those having few 
atoms, are destroyed, and the atoms built together into more complex 
substances, with greater numbers of atoms. The changes are from 
the lower to the higher, ascending, constructive. Now carbonic acid, 
water, and ammonia cannot separate and re-arrange thcmtschc^^ nor can 
they be separated and re-arranged without an enormous expenditure of 



ITS FINAL DESTINATION. 349 

power. Man with his utmost skill cannot imitate the first step in the 
chemistry of the plant. Every green leaf upon the surface of the re- 
volving glohe decomposes carbonic acid every day at the ordinary 
temperatures, setting free the oxygen^ a thing which the chemist cannot 
accomplish with all tlie forces at his command. Nor are we to sup- 
pose that the leaf itself does it ; that cannot originate force any more 
than the water-wheel or the steam-engine ; it must be acted upon. 
Carbonic acid is only decomposed in the leaf during the daytime by 
the power of light ; the effect is produced by solar radiations. All 
true aliments originate under these circumstances in vegetation. 
Though we consume flesh, we only go by the route of another animal 
back to the plant ; our food is all ftxbricated there. Animal life begins 
and is sustained by compounds which are the last and highest product 
of the creative energy of plants. The animal is nourished from its 
blood, but it does not in any sense proG,uce it, it only gives it form ; 
the constituents of blood are generated in plants, stored up in their 
seeds, which are the crowning results of vegetable life, and with the 
maturity of which, most plants employed by man, as food, perish. 
Aliments are thus composed of atoms that have been forced from a 
lower into a higher combination in plants, and in their new state they 
represent the amount of force necessary to place them there. The 
particles of sugar, starch, oil, gluten, &c., are little reservoirs of 
power, resembling bent or coiled springs, which have been wound up 
into organic combination by nothing less than solar enginery. It is 
these materials, dissolved in water, that constitute blood, and with 
which the animal system is kept perpetually charged. The circulating 
medium of the living body is of celestial coinage ; it is a dynamic pro- 
duct of astronomic agencies. The energies of the stellar universe it' 
self are brought into requisition to establish the possible conditions of 
terrestrial life (3). 

661. How Food produces Animal Force. — Food represents force, but 
it is force in a state of equilibrium or rest, just like a pond of water 
enclosed on all sides. But if we make an outlet to the pond, its force 
at once becomes active and available. So the quiescent force of food 
is to become active animal power ; but how ? There enters the vital 
current incessantly from the outward world another stream of matter, 
not solid but gaseous, oxygen from the air, which came by the route of 
the lungs. It is the oflice of this agent to unlock the organic springs 
throughout the vital domain. We have stated before that oxygen is 
an agent of destruction (284); it is tlie foe of the organized state. 
The first step of growth, and the production of food in the leaf, con 



350 PHYSIOLOGICAL EFFECTS OF FOOD. 

Bistedin forcing carbon and hydrogen out of its grasp ; but in the ani- 
mal fabric it is destined to take possession of them again. The food, 
as we have seen, is not destroyed in digestion, it is only dissolved ; but 
in the blood and tissues it is destined to undergo a series of decompo- 
sitions, which are marked by the production of compounds richer and 
richer in oxygen, until finally they are thrown from the body loaded 
to their utmost capacity with this substance. The course of changes 
that characterize.s the animal is descending, from higher to lower, from 
the complex to the simple, from compounds containing comparatively 
little oxygen to those containing much. In this deoc-mposition of ali- 
ment, under the influence of inspired oxygen, bodily force originates. 
We see every day that steam power results from the destruction of 
fuel under the boiler by atmospheric oxygen, and that electric power 
comes from the oxidation or destruction of metal by the liquid in the 
galvanic battery ; but it is equally true that the conditions of human 
power are the oxidation of food and its products in the system. It is 
not from the mere introduction of aliment into the system that we 
obtain strength and nourishment, but from its destruction. A portion 
of food, of course, serves to build up the bodily fabric, but it only 
continues in that state transiently; it is aU finally decomposed and 
dissevered into the simplest inorganic forms. 

662. Dcstruftiye agency of Oxygen. — The body is built of aliment, 
which gives rise by its destruction to force, but the immediate active 
agent which destroys the body, and thus develops force, is oxygen 
withdrawn from the air. From the moment of birth to the moment 
of death, every living animal is incessantly occupied in introducing 
this element into the body to maintain the conditions of force by its 
constant destructive action. If the current of oxygen flowing toward 
a hmb, a muscle, or the brain, be arrested, those parts instantaneously 
lose their power of action. The body of every animal is kept charged 
with this gas every instant of its active existence. If a man is aban- 
doned to the action of air, that is, if no other matter is taken into 
his system, we quickly discover the peculiar agency of oxygen. He 
loses weight at every breath. Inspired oxygen, borne by the arterial 
current, cuts its destructive way through every minutest part, decom- 
posing the constituents of both blood and tissues. The fat is consumed 
first, then the muscular portions, the body becoming reduced and 
emaciated, yet the waste must proceed if life is to last. The brain is 
attacked, its ofiices disturbed, delirium supervenes, and there is an end 
of life. We call this starvation ; it is a conditito in which '* atmos- 
uheric oxygen acts like a sword, which gradually but irresistibly pen- 



ITS FINAL DESTINATION. 351 

etrates to the central point of life, and puts an end to its activity," 
— (LiEBiG,) Had food been regularly introduced, it would have 
opposed a constant resistance to that agent, that is, it would have 
offered itself for destruction and for repair, and thus have protected 
the system from the fatal inroading effects of oxygen. 

663. Combnstion within the Body. — The term combustion is com- 
monly applied to that rapid combination of oxygen with other ele- 
ments, by which a high heat is produced, accompanied with light. 
But the essence of the process is, not its rate^ but the nature and di- 
rection of the changes. It may go forwarc at "ill degrees of speed, 
the effects being less intense the slower it proceeds. The changes that 
go on in the body are the same as tliose in the stove. There is loss of 
oxygen, destruction of combustible matter, oxidized products (car- 
bonic acid and water), and the development of heat, in one case 
rapidly, in the other slowly ; in both cases, in proportion to the amount 
of matter changed. The destruction of aliment in the body is, there- 
fore, a real burning ; a slow, silent, regulated combustion. 

664. All Foods not equally Combnstible. — Foods are destined to be 
burned in the body, but they do not all consume alike. We found it 
necessary, at the outset, to divide the aliments into two great groups, 
based upon their composition — those which contain nitrogen, and 
those which do not. We next found a twofold digestion, in which 
this distinction is recognized ; an acid digestion for nitrogenous mat- 
ters, and an alkaline digestion for the others. And we are now to 
find that this fundamental difference is observed in their final uses, — 
in their relations to oxygen, and modes of destruction. All foods are 
capable of being burned, and are burned ; but there is a wide difference 
in their facility of undergoing this change, and upon that difference 
depends the very existence of the bodily structure. It is clear that if 
certain substances are to be burned in the blood, and others are to es- 
cape from it unburned, the latter must be less combustible than the 
former, or they would aU be consumed together. Accordingly the 
non-nitrogenous bodies, sugar, starch, oil, are easy of combustion ; 
while the albuminous compounds are burned with much greater 
difficulty ; these latter are drawn out of the blood, and used in the 
construction of all the tissues of the system. The bodily structures, 
^vhich require to have a certain degree of permanence, are built of ni- 
trogenous substances, having a low combustibility. The case is roughly 
represented by what occurs in a common stove. Both the fuel and 
tjie stove itself are combustible. The iron is capable of being burned 
up, under proper circumstances, as truly as the wood or coal ; and in 



852 PHYSIOLOGICAL EFFECTS OF FOOD. 

a long time stoves are partially so consumed, or as the phrase is, 
' burned out.' Yet the fuel is so much more easily burned, that the 
iron serves as a structure to retain, enclose, and regulate the combus- 
tion. The difference in capability of burning between the non-nitro- 
genous and the nitrogenous aliments, may not be so great as between 
iron and wood ; yet it is fully sufficient for the purposes of the animal 
economy. 

665, Nitrogen Lowers the Combustibility of Food. — Of all the elements 
of the animal body, nitrogen has the feeblest attraction for oxygen ; 
and what is still more remarkable, it deprives aU combustible ele- 
ments with which it combines, to a greater or less extent, of the 
power of combining with oxygen, or of undergoing combustion. Every 
one knows the extreme combustibility of phosphorus, and of hydrogen ; 
but by combining with nitrogen, they produce compounds entirely 
destitute of combustibility and inflammability under the usual circum- 
stances. Phosphorus takes fire at the heat of the body ; while the 
phosphuret of nitrogen only ignites at a red heat, and in oxygen gaSj 
but does not continue to burn. Ammonia, a compound of nitroget. 
with hydrogen, contains 75 percent., by bulk, of the highly combusti- 
ble hydi-ogen ; but in spite of this large proportion of an element so 
inflammable, ammonia cannot be set on fire at a red heat. Almost all 
compounds of nitrogen are, compared with other bodies, difficultly 
combustible, and are never regarded as fuel, because when they do 
burn, they develop a low degree of heat, not sufficient to raise tlie 
adjacent parts to the kindling point. So with albuminous principles 
in the blood and tissues ; they are placed so low in the scale of com- 
bustibility, that the other group of aliments is attacked and destroyed 
first. " AVithout the powerful resistance which the nitrogenous con- 
stituents of the body, in consequence of their peculiar nature as com- 
pounds of nitrogen, oppose, beyond all other parts, to the action of the 
air, animal life could not subsist. Were the albuminous compounds 
as destructible or liable to alteration by the inhaled "oxygen, as the 
non-nitrogenous substances, the relatively small quantity of it daily 
supplied to the blood by the digestive organs, would quickly disappear, 
and the slightest disturbance of the digestive functions would, ol ne- 
cessity, put an end to life." — (Liebig.) 

666. Heat-prodttcing and Tissue-making Foods. — In considering the 
final uses of foods, we are to i)reserve the distinction with which we 
began. The non-nitrogenous aliments, by their ready attraction for 
exygen, seem devoted to simple combustion in the system, with onlj." 
Jie evolution of heat ; Avhilc the albuminous compounds arc devoted 



PRODUCTION OF BODILY WAEMTH. 353 

to the production of tissue. The first class is hence called the heat- 
producing, calorijjent, or respiratory aliments, while the second is 
designated as the tissue-forming, plastic, or nutritive aliments (430). 
This distinction is to be received with due limitation, for on the ono 
hand, fat, which stands at the head of the heat-producers, is deposited 
and retained in the cells of the tissues, without being immediately con- 
sumed, and probably serves other important purposes beside produc- 
ing heat (722) ; on the other hand, some nitrogenous substances (as 
gelatin, for example,) do not reproduce tissue, while those which are 
worked up into the structure of the system, in their final dissolution, 
minister also to its warmth. These facts, however, do not disturb the 
general proposition. That it is the chief purpose of sugar, starch, veg- 
etable acids, and fat, to be destroyed in the body for the generation 
of warmth ; while albumen, fibrin, and casein, furnish the material for 
tissue, and in their destruction give rise to mechanical force, or animal 
power, — is a fact of great physiological interest and importance, now 
regarded as established, and which was first distinctly enunciated, il- 
lustrated, and confirmed, by Liebkj. 

6, PeodijOtion of Bodily Waemth. 

667. Constant Temperatnrc of the Body. — The influence of tempera- 
ture over chemical transformations is all-controlling ; they are modified, 
hastened, checked, or stopped, by variations in the degrees of heat. 
The living body is characterized by the multiplicity and rapidity of its 
chemical transmutations. Indeed, the whole circle of life-functions 
is dependent upon the absolute precision of rate with which these vi- 
tal changes take place. A standard and unalterable temperature is 
therefore required for the healthy animal organism, as a fundamental, 
controlling condition of vital movements — a certain fixed degree of 
heat to which all the vital operations are adjusted. This standard 
temperature of health in man, or blood heat, varies but slightly from 
98°, the world over. Yet the external temperature is constantly 
changing, daily with the appearance and disappearance of the sun, and 
annually Avith the course of the seasons. "We are accustomed to fre- 
quent and rapid transitions of temperature, from 30 to 60 degrees, by 
the alternations of day and night, sudden changes of weather, and by 
passing from warmed apartments into the cold air of winter. The circle 
of the seasons may expose us to a variation of more than a hundred 
degrees, while the extreme limits of temperature to which man is nat- 
urally sometimes subjected in equatorial midsummer, and arctic mid- 



354 PHYSlOLOGlCAIi EFFECTS OF FOOD. 

winter, embrace a stretch of more than 200° of the thermometric scale. 
Yet through all these thermal vicissitudes, the body of man in health 
varies but little from the constant normal of 98°. 

668. How the Body loses Heat. — In view of these facts, it has been 
maintained that the living body possesses some vital, mysterious, in- 
ternal defence against the influence of external agents; indeed, that it 
is actually emancipated from their effects. But this is wholly errone- 
ous ; the body possesses no such exemption from outward forces ; it is 
a heated mass, which has the same relation to surrounding objects as 
any other heated mass ; when they are hotter than itself it receives 
heat, when they are colder it loses heat ; and the rate of heating or 
cooling depends upon the difference between the temperature of the 
body, and that of the surrounding medium. But in nearly all circum- 
stances, the temperature of the body is higher than the objects around. 
It is, therefore, almost constantly parting with its heat. This is done 
in several ways. The food and water which enters the stomach cold, 
are warmed, and in escaping carry away a portion of the heat. The 
air introduced into the lungs by respiration is warmed to the tempera- 
ture of the body, and hence every expired breath conveys away some 
of the bodily warmth. This loss is variable ; as the temperature of 
the outer air is lower, of course more heat is required to warm it. 
The body also parts with its heat by radiation, just like any other ob- 
ject, and much is likewise lost by the contact of cold air with the skin, 
which conducts it away, a loss which is considerable when the air is 
in motion. This rapid carrying away of heat by air-currents, explains 
why it is that our sensations often indicate a more intense cold than 
the thermometer. But, lastly, the body loses heat faster by evapora- 
tion than in any other way. This takes place from the surface of the 
skin, and from the lungs. About 8i lbs. of water are usually estimated 
to be exhaled in the form of vapor daily, of which one-tlurd escapes 
from the lungs, and two-thirds from the skin, which is stated to have 
28 miles of perspiratory tubing, for water-escape (797). We shall appre- 
ciate the extent of this cooling agency, by recalling what was said of 
the amount of heat swallowed up by vaporization (68). The water of 
the body at 98° receives 114° of sensible heat, and then 1000° of latent 
heat, before it is vaporized ; hence it carries away 1114° of heat from 
the body. 

669. How the Body produces Heat. — To keep the system up to the 
standard point, notwithstanding this rapid and constant loss, there 
must be an active and unremitting source within. Heat-force cannot 
be created out of notliing ; it must have a definite and adequate cause. 



PKODUCTION OF BODILY AVARMTU. 355 

It is by the destruction of food through respiration, that animal heat 
is generated. The main physiological difference between the warm 
and the cold-blooded animals is, that the former breathe actively, 
while the latter do not. It is natural, therefore, to connect together 
the distinctive character of breathing, with the equally distinctive 
character of greater warmth ; to suppose that the incessant breathing 
so necessary to life, is the source of the equally incessant supply of 
heat from within, so necessary also to the continuance of life ; and 
this connection is placed, beyond all doubt, when we attend to the 
physical circumstances by which the change of starch and fat into 
carbonic acid and water is accompanied in the external air. If we 
burn either of these substances in the air or in pure oxygen gas, they 
disappear and ai'e entirely transformed into carbonic acid and water. 
This is what takes place also within the body. But in the air, this 
change is accompanied by a disengagement of heat and light, or, if it 
take place very slowly, of heat alone without visible light. Within 
the body it must be the same. Heat is given off continuously as the 
starch, sugar and fat of the food,, are changed within the body into 
carbonic acid and water. In this, we find the natural source of animal 
heat. Without this supply of heat, the body would soon become 
cold and stiff". The formation of carbonic acid and water, therefore, 
continually goes on ; and when the food ceases to supply the materials, 
the body of the animal itself is burned away, so to speak, that the 
heat may still be kept up. — (Johnstox.) There are certain periods 
in the history of the plant, as germination and flowering, when oxy« 
gen is absorbed, combines with sugar and starch, and produces car- 
bonic acid and water. In these cases, the temperature of the seed 
and the flower at once rises, and becomes independent of the sur- 
rounding medium. 

670. Effect of breathing rarificd Air. — The doctrine, that animal heat 
is due to oxidation in tlie system, is strikingly illustrated by what migh 
be termed starving the respiration. As cold is felt from want of 
food, so also it is felt from want of air. In ascending high mountains, the 
effect upon the system has been graphically expressed as ' a cold to the 
marrow of the bones,' a difficulty of making muscular exertion is ex- 
perienced ; the sti'ongest man can scarcely take a few steps without 
resting ; the operations of the brain are interfered with ; there is a pro- 
pensity to sleep. The explanation of all this is very clear. In the 
accustomed volume of air received at each inspiration, there is a less 
quantity of oxygen in proportion as the altitude gained is higher. 
Fires can scarce be made to burn on such mountain tops ; the air is 



356 PHYSIOLOGICAL EFFECTS OF FOOD. 

too thin and rare to support them ; and so these combustions which 
go on at a measured rate in tlie interior of the body, are greatly re- 
duced in intensity, and leave a sense of penetrating cold. Such jour- 
neys, moreover, illustrate how completely the action of the muscular 
system, and also of the brain, is dependent on the introduction of air 
and under the opposite condition of things, where men descend in 
diving-bells, though surrounded by the chilly influences of the water, 
they experience no corresponding sensation of cold, because they are 
breathing a compressed and condensed atmosphere. — (Dr. Deapee.) 

671. How the unequal demands for Ileat are met. — The steady main- 
tenance of bodily heat being a matter of prime physiological necessity, 
we find it distinctly and largely provided for by a class of foods pre- 
pared in plants and devoted to this purpose. Much the largest por- 
tion of food consumed by herbivorous animals, and generally by man, 
is burned at once in the blood for the production of heat. But there 
are varying demands upon the system at difterent places and seasons, 
and the provision for these is wise and admu'able. First, as the cold 
increases, the atmosphere becomes moi'e dense, the watery vapor is 
reduced to its smallest proportion, and pure air occupies its place, 
so that breathing furnishes to the body a considerably higher per- 
centage of oxygen in winter than in summer, in the colder regions of 
the north, than in the warmer vicinity of the equator. On the other 
hand, there is an important difference among the heat-producing 
principles of food. They vary widely in calorific power. The fats 
and oils head the list ; they consist almost entirely of the two 
highly combustible elements, carbon and hydrogen, containing from 
Y7 to 80 per cent, of the former, to 11 or 12 of the latter. Starch 
occurs next in the series, then the sugars, and lastly the vegetable 
acids and lean meat. Liebig states their relative values, or power 
of keeping the body at the same temperature during equal times, as 
follows : To produce the same effect as 100 parts of fat, 240 of starch 
will be required, 249 of cane sugar, 263 of dry grape sugar and milk 
sugar, and 770 of fresh lean flesh. We shall illustrate this point more 
clearly, w^hen we come to speak of the nutritive value of foods (743). 
A pound of fat thus goes as far in heating as 2f lbs. of starch, or 7^^ lbs. 
of muscular flesh. In regions of severe cold, men instinctively resort 
to food rich in fatty matters, as the blubber and train oil, which are 
the staples of polar diet. Bread, which consists of starch and gluten, 
and which, therefore, as shown by the above illustration, falls far be- 
low oleaginous matter in calorifying power, is found to be very insufll- 
eient in the arctic regions for the maintenance of animal heat. 



PBODUCTION OF BODILY WARMTH. 357 

All breads are, however, not alike in this respect, for the Hudson's 
Bay Traders have found, according to Sir Joiest Eichaedsox, that 
Indian corn bread, which contains about nine per cent, of oil, is de- 
cidedly more supporting than wheaten bread. Dr. Kane, in the nar- 
rative of his last arctic expedition, remarks : " Our journeys have 
taught us the wisdom of the Esquimaux appetite, and there are few 
among us who do not relish a slice of raw blubber, or a chunk of 
frozen walrus beef. The liver of a walrus, eaten with little slices 
of his fat, of a verity it is a delicious morsel. The natives of South 
Greenland prepare themselves for a long journey in the cold by a 
course of frozen seal. At Upernavick they do the same with the 
norwhal, which is thought more heat-making than the seal. In 
Smith's Sound, where the use of raw meats seemed alirost inevitable, 
from the modes of living of the people, Avalrus holds the first rank. 
Certainly, its finely condensed tissue, and delicately permeating fat — 
oh ! call it not blubber — is the very best kind a man can swallow ; it 
became our constant companion whenever we could get it." On the 
contrary, the inhabitants of warmer regions live largely upon fruits, 
which grow there in abundance, and in which the carbonaceous matter, 
according to Likbig, falls as low as 12 per cent. The demands of ap- 
petite seem to correspond closely with the necessities of the system ; 
for while oranges and bread-fruit would be but poor dietetical stuff 
for an Icelander, the "West Indian would hardly accept a dozen tallow 
candles as a breakfast luxury ; but reverse these conditions and both 
are satisfied. A knowledge of the calorifying powers of the various 
elements of food, and of the proportions in which they are foimd, 
enables us to modify our diet according to the varying temperature of 
the seasons. 

672. Regulation of Bodily Temperature. — The question naturally arises, 
why is it that when the external temperature is 100° and even higher 
for a considerable time, and the system is constantly generating ad- 
ditional heat, that it does not accumulate, and elevate unduly the 
bodily temperature? How is it constantly kept down in health to 
the limit of 98° ? This is eftected by the powerful influence of evapo- 
ration from the lungs and skin, already referred to in speaking of the 
way the body loses heat (668). The large amount of water daily 
drank and taken in combination with the food, is used for this pur- 
pose as occasion requires. The lungs exhale vapor quite uniformly, 
but the quantity thrown off from the skin varies with the condition 
af the atmosphere. When the air is hot and dry, evaporation is ac- 
tive, and the cooling efiect consequently greater. During the heat of 



358 PHYSIOLOGICAL, EFFECTS OF FOOD. 

summer, much water evaporates from the skin, and a corresi)ondinglj 
small proportion by the kidneys ; but in the cold of winter there is 
less cutaneous exhalation, the water of the body is not vaporized, but 
chiefly escapes in the liquid form by kidney excretion. As human 
invention has made the steam-engine beautifully automatic and self- 
regulating, and as stoves have been devised which adjust their own 
rate of combustion, and thus equalize the heat, so we find the living 
body endowed with a matchless power of self-adjustment in regard to 
its temperature, by the simplest means, 

673. Houses aud Clothing replace Food. — We have seen that the neces- 
sity for the active generation of heat within the body is in proportion 
to the rapidity of its loss. If the conditions favor its escape, more 
must be produced ; if on the other hand the surrounding temperature 
be high, the loss is diminished, and there is less demand for its evo- 
lution in the body. We have also described the various expedients 
by which heat is i^roduced in our dwellings in winter, thus forming 
an artificial summer climate. Clothing also acts to protect the body 
from loss, and enable it to preserve and economize the heat it gen- 
erates. Hence in winter we infold ourselves in thick non-conducting 
apparel. Clothing and household shelter thus replace aliment ; they 
are the equivalents for a certain amount of food. The shelterless and 
thinly clad require large quantities of food during the cold of winter 
to compensate for the rapid loss of heat. They perish with the same 
supply that would be quite suflicient for such as are adequately clothed 
and well-housed, " It is comparatively easy to be temperate in warm 
climates, or to bear hunger for a long time under the equator ; but 
cold and hunger united very soon produce exhaustion. A starving 
man is soon frozen to death." 

674. Times of Life when Cold is most fatal. — The potent influence of 
temperature upon life must, of course, be most strikingly manifested 
where there is least capability of resistance — in infancy and old age. 
During the first months of infant life the external temperature has a 
very marked influence. It was found in Brussels that the average 
infant mortality of the three summer months being 80, that of January 
is nearly 140, and the average of February and March 125. As the 
constitution attains vigor of development, the influence of seasons 
upon mortality becomes less apparent, so that at the age of from 25 
to 30 years, the diflerence between the summer and winter mortality 
IS very slight. Yet this ditference reappears at a later period in a 
marked degree. As age advances, the power of producing heat de- 
clines, old people draw near the fire and complain that ' their blood is 



PRODUCTION OF BODILY WARMTH. 359 

cliill.' The Brussels statistics show that the mortality oetvveen 50 
and 65 is nearly as great as in early infancy ; and it gradually becomes 
more striking until at the age of 90 and upwards the deaths in Jan- 
uary are 158 for every 74 in July. It has been observed in hospitals 
for the aged, that when the temperature of the rooms they occupy in 
winter sinks two or three degrees below the usual point, by this small 
amount of cooling the death of the oldest and weakest, males as well 
as females, is brought about. They are found lying tranquilly in bed 
without the slightest symptoms of disease, or the usual recognizable 
causes of death. 

675. Diet and the daily changes of Temperature. — The heat of inani- 
mate objects, as stones, trees, &c., rises and falls with the daily varia- 
tions of temperature. The living body would do the same thing if it 
did not produce its own heat independently. If we disturb the calo- 
rifying process, the body becomes immediately subjected to the muta- 
tions of external heat. In starving animals, this temperature rises 
and falls with the daily rise and nightly fall of the thermometer, and 
this response of the living system to external fluctuations of heat is 
more and more prompt and decided as the heat-producing function is 
more and more depressed. As the system is unequally acted upon by 
the daily assaults of cold, it becomes necessary to make provision 
against the periods of severest pressure. In the ever admirable 
arrangements of Providence, the diurnal time of lowest temperature 
is made to coincide with the time of darkness, when animals resort to 
their various shelters to rest and recruit, and are there most perfectly 
protected from cold. Dr. Dkaper has suggested also that the diet of 
civilized man is instinctively regulated with reference to the daily 
variations of temperature. He says : " In human communities there is 
some reason beyond mere custom which has led to the mode of dis- 
tributing the daily meals. A savage may dispatch his glutinous repast 
and then starve for want of food ; but the more delicate constitution 
of the civilized man demands a perfect adjustment of the supply to 
the wants of the system, and that not only as respects the Mnd^ but 
also the time. It seems to be against our instinct to commence the 
morning with a heavy meal. "We Ireah fast, as it is significantly 
termed, but we do no more ; postponing the taking of the chief supply 
until dinner, at the middle or after part of the day. I tliiiik there 
are many reasons for supposing, when we recall the time that must 
elapse between the taking of food and the completion of respiratory 
digestion, tliat this distribution of meals is not so much a matter of 
custom, as an instinctive preparation for the systematic rise and fali 



360 pnysiOLOGiCAL effects of food. 

of temperature attending on the maxima and minima of daily heat. 
The light breakfast has a preparatory reference to noonday, the solid 
dinner to midnight." 

7. Peoductiok of Bodily SxEENCTn. 

676. Amount of mechanical force exerted by the Body. — We have seen 

how the double stream of alimentary and gaseous matter which enters 
the body incessantly gives rise to heat, an agent which we every day 
convert into mechanical power through the medium of the steam engine. 
Sufficient heat is produced in this way annually by an adult man, if it 
were liberated under a boiler, to raise from 25,000 to 30,000 lbs. of 
water from the freezing to the boiling point. But the body also 
generates mechanical force directly, producing effects which present 
themselves to us in a twofold aspect ; those which are involuntary, 
constant, and connected with the maintenance of life, and the volun- 
tary movements which we execute under the direction of the will, 
for multiplied purposes and in numberless forms. That which produces 
movement is force, and there can be no movement without an adequate 
force to impel it. If a load of produce or merchandise is to be trans- 
ported from one place to another, we all understand that force must 
be applied to do it. And so with the human body ; not a particle of 
any of its flowing streams can change place, nor a muscle contract to 
lift the hand or utter a sound, except by the application of force. 
We may form an idea of the amount generated to maintain the invol- 
untary motions essential to life, by recalling for a moment their num- 
ber and extent. We make about nine millions of separate motions of 
breathing, introducing and expelling seven hundred thousand gallons 
of air in the course of a year. At the same time the heart contracts 
and dilates forty millions of times — each time with an estimated force 
of 13 lbs., while the great sanguinary stream that rushes through the 
system is measured by thousands of tons of fluid driven through the 
heart, spread through the lungs, and diffused through the minute ves- 
sels, beside the subordinate currents and side-eddies which traverse 
various portions of the body, and contribute essentially to its action. 
The system not only generates the force indispensable for these effects, 
but also an additional amount which we expend in a thousand forms 
of voluntary physical exercise, labor, amusement, &c. A good laborer 
is assumed to be able to exert sufficient force (expended as in walking) 
to raise the weight of his body through 10,000 feet in a day. Smeaton 
states, tliat working with his arms he can produce an effect equal to 



PRODUCTION OF BODILY STRENGTH. 8G1 

raising 370 lbs. ten feet high, or 3,700 lbs. one foot high in a minute 
for eight hours in the day. 

677. Tissues destroyed in producing Force. — The expenditure of force 
in labor, if not accompanied by a suificiency of food, rapidly wears 
down the system, — there is a loss of matter proportioned to the 
amount of exertion, and which can only be renewed by a correspond- 
ing quantity of nourishment. The parts brought into action during 
exercise are of course those possessing tenacity, firmness, and strength ; 
that is, the tissues and organized structures. The unorganized parts, 
such as w ater and fat, which are without texture, have no vital pro- 
perties, and cannot change their place or relative position by any in- 
herent capability. It is the bodily tissues that are called into action, 
and these undergo decomposition or metamorphosis in the exact ratio 
of their active exercise. We have stated that the motions within the 
system are numerous and constant. If we look on a man externally, 
he is never wholly at rest ; even in sleep there is scarcely an organ 
which is not in movement or the seat of incessant motion ; yet the 
destruction of parts is correspondingly active. It may vary perhaps 
in different constitutions, in different parts of the system, and under 
various circumstances, but it goes on at a rate of which we are hardly 
conscious. Chossat ascertained the waste in various animals to be an 
average of l-2'4th part of their total weight daily ; and Schmidt deter- 
mined it to be, in the case of the human being, l-23d of the weight. 
Professor Johnston says : " An animal when fasting will lose from a 
fourteenth to a twelfth of its whole weight in twenty-four hours. 
The waste proceeds so rapidly that the whole body is now believed 
to be renewed in an average period of not more than thirty days. 

678. Destination of the Kitrogenons Principles. — The basis of animal 
tissue is nitrogen. The muscular masses are identical in composition 
with the nitrogenous principles of food, albumen, casein, gluten. 
Those substances have, by digestion, become soluble; that is, they 
have all assumed the form of albumen, and thus enter the blood. In 
this liquid, whose prime function is to nourish the system, albumen is 
always present in considerable quantity. When the fibrin and red- 
coloring matter (clot) is removed from blood, the watery serum or 
plasma remains, containing albumen, wliich coagulates like white of 
egg by heat. Albumen is the universal starting point of animal nutri- 
tion ; it is the liquid basis of tissue and bodily development through- 
out the entire animal kingdom. We see this strikingly illustrated by 
what takes place in the bird's egg during incubation. Under the in- 
fluence of warmth, and by the action of oxygen, which enters through 

16 



362 PHYSIOLOGICAL EFFECTS OF FOOD. 

the porous shell, under the influence therefore of the same conditions 
which accompany respiration, all the tissues, membranes and bones, 
(by the aid of lime from the shell,) are developed. The foundation 
material from which they are all derived is albumen, and it is the 
same with the growth and constant reproduction of our own bodies 
during life. The course of transformation by which albumen is con- 
verted into the various bodily tissues, has not yet been certainly 
traced. But it is now universally agreed that it is the nitrogenous 
principles of food, — those of low combustibility, which are employed 
for the nutrition of animal structures — the reparation of tissue-waste. 
Those substances furnish the instruments of movement, and minister 
directly to the production of mechanical force. Their design is two- 
fold, to form and maintain the bodily parts in strength and integrity, 
and to be finally destroyed for the development of power. 

679. Actioa of Oxygen upon the Tissaes, — Oxygen plays the same im- 
portant part in tissue destruction as in the simple development of heat 
by combustion of respiratory food. It is the agent by which the 
moving parts are decomposed and disintegrated. The muscles are 
paralyzed if the supply of arterial blood containing the oxygen which 
is to change them, and the nutritive matter which is to renew them, 
be cut off. On the other hand, if there is rapid muscular exercise 
and consequent waste, the circulation is increased and the breathing 
quickened, by which the supply of oxygen is augmented. The 
changes of the tissues in action are, moreover, retrogressive, and 
downwards to simpler and simpler conditions. The products of 
metamorphosis are oxidized, and then made soluble in the blood by 
which they are promptly conveyed away, and thrown out of the body 
by the liquid excretion. It is thus that oxygen, by slow corrosion and 
burning of the constituents of the muscles, gives rise to mechanical 
force. But oxidation is invariably a cause of heat ; decomposition of 
the tissues, therefore, must develop heat at the same time with me- 
chanical effect. Indeed, violent muscular exercise is often resorted to 
in winter as a source of bodily warmth, by increasing the respirations 
and muscular waste. In this subordinate way, the nitrogenous ali- 
ments become heat-producers. It is not to be supposed that oxygen 
seizes upon all the atoms of tissue indiscriminately, or upon those 
which it finds next before it. There is a wonderful selective power, 
6ome particles are taken and others left. Those only are seized upon 
which in some unknown way, perhaps under the regidating influence 
of the nervous system, are made ready for change. 

680. Relation between Waste and Supply. — If an organ or part be the 



PRODUCTION OF BODILY STEENGTH, 363 

seat of destructive and reparative changes, and its weight remains in- 
variable, we know that an exact balance is struck between these two 
kinds of transformation. But the processes of destruction and reno- 
vation in the body are not necessarily equal, so that every atom that 
perishes out of the structure is promptly replaced by another. In 
those cases where the system neither gains nor loses weight, the an- 
tagonist forces must of course precisely compensate each other. Yet, 
even here, the general equilibrium is the result of constant oscillations. 
The involuntary muscles, which play continually, as those of the heart, 
and the muscles engaged in respiration, have an intermitting action. 
The short or momentary period of activity is followed by a corre- 
sponding interval of rest. If the first condition involves destruction, 
the second allows of nutrition. That portion of the mechanism which 
is independent of voluntary control, is thus self-sustaining. Still, in 
the case of these parts, the equipoise between waste and supply may be 
lost, as in bodily growth when nutrition exceeds decomposition, or in 
deficiency of nutriment, when destruction proceeds at the expense of 
the tissue, which loses weight faster than the food renews it. As re- 
gards the waste and renovation attending voluntary movement, there 
is the same periodicity. Destruction gains upon nutrition during the 
exercise of the day, and what was lost is regained by nutrition during 
rest at night. In sleep, nutrition is at its height while waste falls to its 
miniumm. As bodily exertion costs tissue destruction, which can only 
be made good again by albuminous substances, it foUows that these will 
be demanded for food, in proportion to the amount of eflort expended. 
If such food be not adequately supplied, or if from any cause the body 
be incapable of digesting or assimilating it, the apparatus of force begins 
at once to give way, the acting tissues shrink and fail, for human effort is 
carnivorous^ fiesh-consuming. If, on the other hand, the system is main- 
tained at rest, that is, if force is not exerted, the nutriment is not used 
or expended, but is laid up in the body, and serves to increase the mass. 
681 . Hastening and retarding tissue changes. — Ingested substances have 
a twofold relation to waste or metamorphosis of the tissues. Some, 
as we have seen, become portions of the animal solids, and then un- 
dergo transformation. Others have the power of modifying or con- 
trolling these changes, without in the same way participating in tliem. 
Some of these increase metamorphosis, and others checlc it. Common 
salt, for example, and an excess of water, act as hasteners of tissue 
change, while alcohol and tea act as arresters of metamorphosis. If 
we consume those substances which augment the waste, it is said wo 
require a fuller diet to compensate for the extra loss, or the body de« 



364 PHYSIOLOGICAL EFFECTS OF FOOD. 

clines in weight with more rapidity than otherwise. If we employ the 
arresters of metamorphosis, we are supposed to have tissue, and can 
maintain our usual strength and weight on a more slender diet. That 
certain substances produce these eflects, may be regarded as establish- 
ed, but it cannot be admitted that they are proper aliments. We re- 
cognize transformation of the living parts, as the highest and final 
physiological fact, the necessary condition of human activity. Dr. 
Chambeks remarks — " Metamorphosis is Z(/e, or an inseparable part 
of life." Undoubtedly the rates of bodily change are liable to certain 
variations, within limits of health ; but the whole import of the vital 
economy, leads us to connect accelerated and retarded changes with 
variations in the exercise of force, by a fixed organic ordinance. With 
high activity, a rapid change, and with rest, a minimum of loss is evi- 
dently nature's purpose, and her law. Substances introduced into the 
system, which act upon the tissues, as it were from Avitliout, and in- 
terfere with this fundamental relation between rate of exertion and 
rate of change, can be regarded in no other light than as disturbers of 
physiological harmony. Still, we are to be cautious about theoretically 
prejudging any substance ; whether it be beneficial or injurious is as- 
certainable only by careful observation and experience of its effects. 

8. MiXD, Body, and Aliment. 

682. Mind brought into relation with Matter. — In his ultimate destiny, 
we contemplate man as an immortal spirit, but in the Divine arrange- 
ment, that .spirit is to be educated and prepared in nature and time for 
its onward career. Spirit or mind partakes in nothing of the attri- 
butes of matter, but it corresponds closely to our conception of force. 
The passions are regarded as the mind's motors^ or motive powers. 
The directive or governing element we call will^ or will-power. We 
speak constantly of intellectual force, and mental energy, and regard 
the mind as an assemblage of faculties or powers capable of producing 
effects. Indeed, as we consider the Mind or Will of God to be the all- 
controliing activity of the universe, so the mind of man, created in hia 
Maker's image, is perpetually demonstrating an over-mastering con- 
trol of tiie elements and agencies of nature. As mind is thus designed 
to be developed by action, with the material world for its theatre, it 
must of course bo brought into relation with matter. The brain is the 
consecrated part where this inscrutable union is eficcted, and the ner- 
vous system is the immediate mechanism which establishes a dynamic 
connection between the spiritual intelligence and the physical creation. 

668. Mental Exercise destroys Nervous Matter. — Of the nature of this 



MIND, BODY, AND ALIMENT. 3G5 

union, horo it is accomplished, we know nothing, but some of its con- 
ditions are understood. We are certain that the brain and nerves 
wear and waste by exercise, and require renewal, just like all the 
other tissues. Nervous matter in this respect is no exception to the 
general law of the organism. The external universe pours in its im- 
pulses through all the avenues of sense, along the nerve routes to the cen- 
tral seat of consciousness, the brain ; while the mind, exerting itself 
through that organ, and another system of nerves, calls the muscles into 
action, and produces its thousand-fold effects upon external objects. In 
both cases there is decomposition and loss of nerve-substance, and 
there must, therefore, be a nutrition of brain and nerves, as truly as 
of any other part ; nay, more truly, for destruction and renovation 
are perhaps more active in these parts than in any others. Arterial 
blood, with its agent of disorganization (oxygen), and its materials of 
repair, are sent to the brain in a far more copious flood than to any 
other equal portion of the body. Blood-vessels are also distributed 
most abundantly around the nerves, so as to effect their nutrition in a 
perfect manner; while if the vital stream be checked or arrested, the 
nerve loses its power of conducting impressions, and the brain its 
capacity of being acted upon by the mind ; the interruption of the 
blood-stream through this organ producing instantaneous unconscious- 
ness. Besides, the nerve-tissue consists of the most changeable mate- 
rials, 70 to 80 per cent, water, 10 of albumen, and 5 to 8 of a peculiar 
oily or fatty substance, with various salts. It is interesting to re- 
mark, that in starvation the parts are disorganized and consumed in 
the inverse order of their physiological values. First, that which is 
of lowest service, and can be best spared; the fatty deposits are 
wasted away, then the muscular and cellular tissues, and lastly the 
nervous system, which remains undisturbed and intact until the dis- 
organization of other parts is far advanced. The mind's throne is the 
last part invaded, and the last to be overturned. "We are struck with 
the wisdom of this arrangement, but we cannot explain it. 

684. Can we measure Brain and Nerve waste ? — The appropriation of 
certain specific parts to certain purposes, is the basal fact of physiolo- 
gy. A part may indeed perform several offices, but they are determi- 
nate and limited, and the different portions cannot change duties ; the 
stomach cannot respire, nor the lungs digest, the mind cannot act di- 
rectly upon the muscular system (only through the intermedium of 
the nerves), nor can the nerves exert mechanical force. Each part^ 
therefore, does its appropriate work ; and as it has a special composi- 
tion, its metamorphosis gives rise to peculiar products. Muscular de- 



i^GG niYSIOLOGlCAL EFFECTS OF FOOD. 

composition must hence yield one set of substances, and nerve-waste 
another. It has been attempted to identify these products, and thus 
get indications of the amount of change in each part, as a measure of 
the degi'ee of its exercise. But the results yet obtained are probably 
only approaches to the truth. Thus, urea is undoubtedly a result of 
muscular change, and some have regarded its amount in the renal ex- 
cretion as an index to the degi'ce of muscular exercise. But others 
affirm that it may also come from unassimUated food, as well as active 
muscle, which casts a doubt over conclusions thus formed. In +he 
same Avay, salts of phosphoric acid have been regarded as the peculiar 
jjroducts of brain and nerve waste, and their amount in the kidney 
evacuations, as a measure of the exercise of brain and nerves. From 
the researches of Dr. Bexsk Joxes, it appeared that where there is a 
periodical demand upon the mental powers (as among clergymen, for 
example, in preparation for their Sunday exercises), there is a corre- 
sponding rise in the quantity of alkaline phosphates voided by the renal 
organs. Yet here, too, there is uncertainty, for we are not sure that 
these phosphatic salts may not have other sources also. 

685. The Mind's action wears and exhausts the Body. — That all forms of 
mental exertion have a wearing, exhausting effect upon the body, 
producing hunger, and a requirement for food, is well known. Pure 
intellectual labor, vigorous exercise of the will, active imagination, 
sustained attention, protracted thought, close reasoning, ' the nobler 
enthusiasms, the afflatus of the poet, the ambition of the patriot, the 
abstraction of the scholar,' — the passions and impulses, hope, joy, 
anger, love, suspended expectance, sorrow, anxiety, and 'corroding 
cares,' all tend to produce physical exhaustion, either by increasing 
the destruction of the tissues, or preventing the assimilation of nutri- 
ment. It is true that the stunning effect of an emotion, a surge of 
joy, or a blast of anger, or profound grief, may temporarily overpower 
the sensation of hunger, that is, prevent its being felt, but after a time 
the appetite returns with augmented force. In sleep, the mechanism 
of sense, consciousness, volition, and passion, is at rest, and unhindered 
nutrition makes up for the losses of the waking hours. If the brain 
be overworked, either %y long and harassing anxiety, or by severe 
and continued study, it may give way ; that is, its nutrition takes place 
BO imperfectly as to produce morbid and unsound tissue, which can 
only be restored to the healthy state by long mental tranquillity and 
cessation of effort. 

686. The Phosphatic constituents of Brain. — We have spoken of the 
phosphates as special products of brain and nerve waste. That phos- 



MIND, IK)DY, AND ALIMENT. 367 

phorus, iu some state, or combination, is a leading ingredient of uervona 
and cerebral matter, is unquestionable ; and that it stands related in 
some way to the fundamental exercise of those parts, will hardly be 
doubted. We remember that it is a very remarkable element, 
shining in the dark (from which it takes its name), and having a most 
powerful attraction for oxygen, combining with a large amount of it, 
and generating. phosphoric acid with intense heat <ind light. It is 
also capable of existing in two states ; its ordinary active condition 
and a passive or inert state, in which it seems paralyzed or asleep, and 
exhibits no affinity for oxygen. The solar rays have the power of 
throwing it from tlie active to the passive form. It has been main- 
tained that in the leaf and by the sun, elementary phosphorus is sepa- 
rated from its compounds, put iu the passive state, rocked to sleep (297), 
is stored up iu foods, and thus finds its way into the body, its blood and 
nervous matter, — and that finally, in the exercise of mental and ner- 
vous power, it resumes the active condition, and undergoes oxidation, 
producing phosj)horic acid. In L'Hekitiee's analysis of nervous mat- 
ter (quoted by standard physiological authorities), it is stated that the 
proportion of phosphorus iu infants is 0'80 parts per 1,000, in youths' 
1*65 (more than double), in adults 1'80, in aged persons I'OO, and in 
idiots 0'85, thus appareutly connecting the quantity of this substance 
in the brain with maturity and vigor of mental exercise. From this 
point of view Dr. Moleshott leaps at once to the conclusion, ' no 
phosphorus, no thought ;' Liebig, however, denies point-blanc that 
elementary phosphorus has ever been found in nervous matter. He 
says, " no evidence is known to science tending to prove that the food 
of man contains phosphorus, as sucJi, in a form analogous to that in 
which sulphur occurs in it. No one has ever yet detected phosphorus 
in any part of the body, of the brain, or of the food, in any other 
form than that of phosphoric acid." As phosphorus and phosphoric 
acid, in their properties, are as wide asunder as the poles of the earth, 
it is highly incorrect to use the terms interchangeably, or (according to 
the statement of Liebig) to apply the term phosphorus in this con- 
nection. It may be remarked that the phosphoric compound is a con- 
etituent of the oily matters of nerve tissue, which are hence called 
' pbosphorized fats.' 

687. Are there speciat Brain Natriments. — On the strength of this 
phosphoric hypothesis, crude suggestions have been volunteered for 
students and thinkers, to take food abounding iu phosphorus, as fish, 
eggs, milk, oysters, &c. Such advice has no justification in well de« 
termined facts. We are not authorized by science to prescribe a diet 



368 PHYSIOLOGICAIi EFFECTS OF FOOD. 

specially or peculiarly constructed to promote brain nutrition and pro- 
tract mental exercise. But wliile it wonld seem as if care had been 
taken to secure these high results in the universal constitution of food, 
still it is certainly in accordance with analogy, that specific aliments 
should be adapted, or at all events hest adapted, to produce certain 
kinds of effect in the system. Special means for special ends make up 
the unitary scheme of the living economy. The waste produced by 
mental exertion is repaired only by food, but to say by all food alike 
transcends the warrant of science. Professor Liebig remarks, " It is 
certain that three men, one of whom has had a full meal of beef and 
bread, the second cheese or salt fish, and the third potatoes, regard a 
difficulty which presents itself from entirely different points of view. 
The effect of the different articles of food on the brain and nervous 
system is different, according to certain constituents peculiar to each 
of these forms of food. A bear kept in the anatomical department of 
this university, exhibited a very gentle character as long as he was fed 
exclusively on bread. A few days' feeding with flesh rendered him 
savage, prone to bite, and even dangerous to his keeper. The carni- 
vora are, in general, stronger, bolder, and more pugnacious than the 
herbivorous animals on which they prey ; in like manner those nations 
which live on vegetable food differ in disposition from those which 
live chiefly on flesh. The unequal effects of different kinds of food, 
with regard to the bodily and mental functions of man, and the de- 
pendence of these on physiological causes, are indisputable; but as yet 
the attempt has hardly been made to explain these differences accord- 
ing to the rules of scientific research." 

688. Diet of Brain-workers. — Yet the diet of the literary, of artists, 
and those who devote themselves to intellectual labor, is by no means 
unimportant, and should be carefully conformed to their peculiar cir- 
cumstances. They should avoid the mistake of supposing that, as they 
do not work physically, it is no matter how slight their diet, and the 
perhaps still more frequent error, on the other hand, of excessive eat- 
ing, the fruitful cause of dyspepsia, and numerous ailments of the sed- 
entary. The best condition of mind corresponds with the most 
healthy and vigorous state of body. The blood prepared by the di- 
gestive and pulmonary organs, and taking as it were its quality and 
temper from the general state of the system, nourishes the brain and 
influences the mind. That diet and regimen are therefore best for 
thinkers, which maintain tlie body in the most perfect order. They 
should select nutritious and easily digestible food, avoiding the more 
refractory aliments, leguminous seeds, heavy bread, rich pastry, «fec. 



INFLUENCE OF SPECIAL SUBSTANCES. 369 

689. Dlen seek for Braia Excitants. — Although specific brain nntri- 
ents and thoiigbt-sustainers are not determined among foods, yet sub- 
stances exerting a powerful influence through the brain upon the mind, 
are but too well known. By a kind of ubiquitous instinct, men have 
ransacked nature in quest of agents which are capable of influencing 
their mental and emotive states, and they have found them every 
where. It is estimated that the peculiar narcotic resin of Indian 
hemp {hascJiish\ is chewed and smoked among from two to three hun- 
dred millions of men. The letel nut is employed in the same way 
among a hundred millions of people ; the use of opium j^revails among 
four hundred millions, and of tobacco among eight hundred million 
of the world's inhabitants. These substances act powerfully, although 
somewhat differently, upon the nervous system, and thus directly affect 
the state of the mind and feelings. "We here touch upon the myste- 
rious world problem oi narcotism ; but its discussion, though of absoib- 
ing interest, would be too extensive for our limits, besides being for- 
eign to the present inquiry, which is restricted to the general subject 
of foods. The effects of tea and coffee will be noticed when speaking 
of drmks (704). 

9. Ikflttenoe of Special SimsTANOES. 
A.— Saline Matters. 

690. The Ash elements of Food essential to Life. — When vegetable sub- 
stances are burned, there remains a small portion of incombustible 
mineral matter. It was formerly thought that this consisted merely 
of contaminations from the soO, which happened to be dissolved by 
water that entered the roots, and was therefore present in the vegeta- 
ble by accident. "We now understand that such is far from being the 
fact. The ash-principles of food are indispensable to animal life. In- 
deed, without them neither group of the alimentary substances which 
we have been considering could do its work. It has been found, in 
numerous experiments, made upon the lower animals, that neither 
gluten, casein, albumen, sugar, oil, nor even a mixture of these, when 
deprived as far as possible of their mineral ingredients, are capable of 
sustaining life ; the animal thus fed actually perishes of starvation. 

691. Acids, Alkalies, Salts. — We remember that acids are bodies hav- 
ing the power of turning blue test paper red, and that alkalies change 
the red to blue. They also combine together, each losing its peculiar 
properties, and produce salts. If the properties of the acid and alkali 
both disappear, the salt produced is neutral^ that is, neither acid nor 

16* 



370 PHYSIOLOGICAL EFFECTS OF FOOD. 

alkaline. If the acid bo stronger, or there be a double or treble dos« 
of it combining -with tlie alkali, the compound is still acid, an acid 
salt; or if the alkali be strongest or in excess, it overpowers the acid 
and an alhaline salt results. If a neutral salt be dissolved in water, 
the liquid will be neither acid nor alkaline. If an acid salt be dis- 
solved, the water will be acidulous, and produce all the effects of 
acidity ; if an alkaline salt, the liquid will be alkaline, producing alka- 
line effects. The ash of foods consists of potash, soda, lime, magnesia, 
oxide of iron, sulphuric, carbonic and phosphoric acids, silica and com- 
mon salt. Fruits abound in acid salts, that is, powerful organic acids, 
as oxalic, tartaric, and malic acids, with potash and lime ; the acids be- 
ing in excess. When fruits are burned, the organic acids are consumed 
or converted into carbonic acid, and the salts become carbonates — neu- 
tral carbonates of lime or alkaline carbonates of potash. The quanti- 
ties of salts, alkalies, and alkaline earths contained in many kitchen 
vegetables are surprising. Celery (dried), contains from 16 to 20 per 
cent., common salad 23 to 24 per cent., and cabbage heads 10 percent. 

692. The Ashes of the Food arc Assimilated. — When the organic mat- 
ter of food is burned away in the system, a residue of ashes is left, 
just as in open combustion in the air. But they are not cast at once 
from the body as useless, foreign, or waste matters. They have im- 
portant duties to perform as mineral substances, after being set free 
from organized compounds ; and they hence remain dissolved in the 
blood and various juices of the system. Portions of these mineral 
matters are constantly withdrawn from the circulation, some at one 
point and some at others, to contribute to special local nutrition. 
Thus phosphate of lime is selected to promote the growth of bones, 
while the muscles withdraw the phosphates of magnesia and potash ; 
the cartilages appropriate soda in preference to potash ; silica is se- 
lected by the hair, skin, and nails ; while iron is attracted to the red 
coloring matter of the blood, and the black coloring matter within 
the eye. 

693. The Blood Alkaline, and why T — But there remains constantly 
dissolved in the blood and animal juices, a proportion of acids, al- 
kalies, and salts, which impart to these liquids either acid or alkaline 
properties. The result, however, is not left to accident. Whether 
a liquid be acid or alkaline is of essential importance in refer- 
ence to the offices it has to perform. We have seen that it is 
the determining fact of the digestive juices; one is always acid, and 
the other alkaline, and their peculiar powers depend upon these 
properties. So with the blood. It contains potash, soda, lime, mag- 



INFLUENCE OF SPECIAL StJESTAIfCES. 371 

nosia, oxide of iron, phosphoric acid, and common salt ; yet these are 
so proportioned that soda is in excess, and hence the blood of all animals 
is invariably alkaline. An alkaline condition is indispensable to the 
action of this fluid. Liebig remarks, " The free alkali gives to the 
blood a number of very remarkable properties. By its means the 
chief constituents of the blood are kept in their fluid state, the ex- 
treme facility with which the blood moves through the minutest ves- 
sels, is due to the small degree of permeability of the walls of these 
vessels for the alkaline fluid. The free alkali acts as a resistance to many 
causes, which, in the absence of the alkali, would coagulate the albu- 
men. The more alkali the blood contains, the higher is the tempera- 
ture at which its albumen coagulates ; and with a certain amount of 
alkali, the blood is no longer coagulated by heat at all. On the al- 
kali depends a remarkable property of the blood, that of dissolving 
the oxides of iron, which are ingredients of its coloring matter, as 
well as other metallic oxides so as to form perfectly transparent solu- 
tions." Alkali in the blood also promotes the oxidation of its consti- 
tuents. A number of organic compounds acquire by contact with, or 
in presence of, a free alkali, the power of combining with oxygen 
(burning), which alone they do not at all possess at the ordinary 
temperature of the air, or at that of the body. — (Cheverul.) The 
alkalies of the blood exert a precisely similar action, increasing the 
combustibility of the respiratory foods. 

694. Flesh and its Jnices, Add. — But while alkali is necessary to 
maintain the perfect fluidity and combustive relations of the blood, 
the alkaline state seems unfavorable to nutrition. In the ash of 
muscles, there is an excess of phosphoric acid, and the juice of flesh 
which surrounds the muscles is also acidulous. The blood nourishes 
the flesh-juice, and that the muscles, but an acid medium is indis- 
pensable to the latter change. Taking the whole body together, acids 
predominate, so that-if the blood were mingled with the other juice, 
the whole would liave an acid character. The chief flesh acids are 
l)hosphoric and lactic, but how they influence nutrition is not under- 
stood. The remarkable fact of the existence in all parts of the body 
of an alkaline liquid, the blood, and an acid liquid, the juice of flesh, 
separated by very thin membraucs, and in contact with muscles and 
nerves, seems to have some relation to the fact now established, of the 
existence of electric currents in the body. 

695. Uses of Salt in the System.— The properties of commercial or 
common salt, have been noticed when speaking of its preservative 
powers (590). We may now consider its action in the system. It la 



372 PHYSIOLOGICAL EFFECTS OF FOOD. 

a large and constant ingi-edient of the blood, forming nearly sixty pel 
cent, of its ash. It exists also in other fluids of the body, but is not, 
perhaps, a constituent of the solid tissues, except the cartilages. Its 
offices in the system are of the first importance. It increases the so- 
lubility of albuminous matters. Dissolved in the liquids of the ali- 
mentary canal, it carries with it their important principles, preserves 
them fluid through the chyle and blood, then parting from them as 
they become fixed in the tissues, returns to perform the same round 
again. By decomposition in presence of water, common salt yields 
an acid and an alkali, hydrochloric acid and soda. This separation is 
is effected in the system, indeed there is no other soui'ce for the hy- 
drochloric acid of stomach digestion. The considerable quantity of 
soda in the bile and pancreatic juice, which serve for intestinal diges- 
tion, as well as the soda of the alkaline blood, are chiefly derived from 
common salt. A portion comes directly from the food, but by no 
means sufficient for the wants of the body. Yet it is highly probable, 
that in the econony of the system, the same materials are used over 
and over, the acid of the stomach, as it flows into the intestine, com- 
bining with the soda it finds there, and reproducing common salt, 
which is absorbed into the blood, decomposed, and yielded again to 
the digestive organs. We recollect that common salt consists of 
chlorine and sodium ; it is a cTiloride of sodkim. Chloride oi 2yotassium 
is another salt of apparently quite similar properties. Yet in their 
physiological effects, they are so different, that while chloride of 
sodium exists largely in the blood, it is not present in muscles or juico 
of fiesh, chloride of potassium being found there. They seem to have 
distinct and different offices, and are not replaceable. But the chlo- 
rine of the chloride of potassium comes from common salt. It may 
be remarked, that as phosphate of soda exists in the blood, phosphate 
of potash belongs to flesh-juice and muscles. 

696. Common Salt contained in Food. — Salt escapes from the system 
by the kidneys, intestines, mucus, perspiration, and tears. To re- 
place this constant loss, and maintain the required quantity in the 
body, there must be a proper supply. It is universally diffused in 
nature, so that we obtain it both in the solid food Ave consume and in 
the water we drink, though not always in quantity sufficient for the 
demands of the system. Yet the proportion we obtain in food is 
variable, animal diet containing more than vegetable ; though the 
parts which most abound in this ingredient, — the blood and carti- 
lages — are not commonly used for food. Of vegetable foods, seeds 
contain the least amount of common salt, roots vary in their quantity, 



INFLUENCE OF SPECIAL BTJBSTANCES. 372 

turnips having hardly a trace. Yet much depends upon its abundance 
in the soil, and even in the atmosphere ; the air near tlie sea being 
saline from salt vapor. Plants near the sea are richer in soda than 
those grown inland, the latter abounding in potash. When we reflect 
upon the importance of the duties of salt in the organism, and that its 
necessary proportion in the blood is so much larger than in the food, — 
often tenfold greater — and besides, that its quantity is extremely vari- 
able in our aliments, its almost universal use as a condiment, will not 
surprise us. The craving for it is very general — probably instinctive 
— but where it does not exist, we conclude, either that sufficient is 
furnished naturally in the food and drink, or that animals suffer for 
the want of it. The quantity annually consumed by each individual 
in France, has been estimated at 19^ lbs; in England at 22 lbs. 

697. Effects of too little and too much Salt. — ^From what has been 
said, we see that a due supply of salt is of the first necessity ; its de- 
ficiency in diet can only prove injurious. The most distressing symp- 
toms, ending in death, are stated as the consequence of the protracted 
use of saltless food. The ancient laws of Holland "ordained men to 
be kept on bread alone, nnmixed with salt, as the severest punish- 
ment that could be inflicted upon them in their moist climate ; the 
effect was horrible ; — these wretched criminals are said to have been 
devoured by worms engendered in their own stomachs." Taken into 
the system in large quantity (a table spoonful), it excites vomiting ; 
when thrown into the large intestines, it purges. A too free use of 
salt engenders thii-st ; in moderate quantities, it increases the appetite 
and aids digestion. A long course of diet on provisions exclusively 
salt-preserved, produces the disease called scurvy. This condition of 
body is believed by some to be due to a deficiency of potash com 
pounds in the system, as in the act of salting, various valuable ali 
ments are abstracted (593). Potatoes, and vegetables rich in potash 
are excellent antiscorhutics — correctives of scurvy. Fresh flesh yieldr 
potash to the system unequally ; for in that of the ox, there is three 
times, in that of the fowl, four times, and in that of the pike, five times 
as mucli potash as soda. Experiments relating to the infiuence of com- 
mon salt upon animals, have given somewhat discordant results. In 
some cases, it improved their appearance and condition decidedly ; 
while in others, no such result followed. Yet the amount supplied 
naturally in the food, in the several instances, was not determined. 
Salt is supposed to be in some way closely allied to the nutritive 
changes, and some think it increases the metamorpliosis of the 
body ; so that a free use of it would only be consistent with a liberal 
diet. 



374 niYsiOLOGiCAL effects of food. 

698. Carbonates of Soda and Potash. — The exclusive employment of 

these substances in extemporising light bread (509), makes a reference 
to their physiological action necessary. Carbonate of potash in its 
crude shape, appears as pcarlash; in its more purified form it hsaleratus. 
Crude soda is known as sal-soda or soda-saleratus ; refined and cleared 
of its chief impurities, it forms carbonate and bicarbonate of soda. 
All these compounds have the common alkaline or burning property, 
which belongs to free potash and soda ; but it is lowered or weakened 
Dy the carbonic acid united with them. The potash compounds are 
the strongest, those of soda being of the same nature but weaker. Yet 
the system, as we have just seen, recognizes essential differences be- 
tween them ; one pertains to the blood and the other to the flesh. 
According to the theory of their general use for raising bread, they 
ought to be neutralized by an acid, mm-iatic, tartaric, acetic, or lactic, 
thug losing their peculiar properties and becoming salts. Tbese 
changes do take place to a certain extent, and the saline compounds 
formed, are much less powerful and noxious than the nnneutralized 
alkalies ; their effects are moderately laxative. Yet, in the common 
use of these substances, as we have stated, the alkali is not all ex- 
tinguished ; much of it enters the system in its active form. Pure, 
strong potash, is a powerful corrosive poison ; disorganizing the 
stomach, and dissolving its way through its coats, quicker, pei'haps, 
than any other poisonous agent. "When the alkalies are taken in small 
quantities, as where there is an excess in bread, they disturb healthy 
digestion in the stomach, by neutralizing its necessary acids (643). 
They are sometimes found agreeable as palliatives, where there is 
undue acidity of the stomach ; and, on the other hand, they may be 
of service in the digestion and absorption of fatty substances. It ia 
alleged that their continued use tends to reduce the proportion of tho 
fibrin in the blood. Cases are stated, where families have been poisoned 
by the excessive employment of saleratus. 

B.— Liiauid Aliments. 

699. Physiological importance of Water. — Water is the most abundant 
compound in the body, constituting 80 per cent, of the blood, and 75 
per cent, of the whole system,' — in importance to life it ranks next 
to oxygen of respiration. An adult man takes into his system three- 
quarters of a ton of it in a year. It supplies some of the first condi- 
timis of nutrition, and is, thereft)re, entitled to head the list of aliments 
(oliH). It is the simple and universal beverage furnished by nature, for 
all H\ing beings, and exists in greater or less proportion, as we have 



mFLUENCE OP SPECIAL SUBSTANCES. 375 

Been, ia all solid food. Vegetables and meats are, at least, tliree- 
fourths water ; while bread is about 45 per cent, or nearly one half. 
Athongh there is a little water even in the dryest food, yet the demand 
for it is so great, and its consumption so rapid, that our mixed ali- 
ments do not furnish sufficient, while the most nutritious, are the most 
provocative of thirst. Hence, we daily drink large quantities of it in 
the free or liquid condition. 

700. Its twofold state in the body. — Water exists in the body, in the 
fluctuating, circulating, liquid condition ; and also fixed as a solid in the 
tissues. In the liquid state, it subserves the same great purpose 's 
in the world of commerce, it is an agent of transportation. Its par- 
ticles glide so freely among each other, as easily to be put in motion, 
which makes it a perfect medium of circulation, and transportation of 
atoms. It is the largest constituent of the fleshy parts, serving to 
give them fulness, softness, and pliancy. "Water is a vital and essen- 
tial portion of the animal structure, but hardly an organized constitu- 
ent. It is intimately absorbed and held in a peculiar mechanical 
combination, whicli permits of separation by pressure. " The milk- 
white color of cartilage, the transparency of the cornea, the flexibility 
and elasticity of muscular fibre, and the silky lustre of tendons, all 
depend on a fixed proportion of water in each case." 

701. Water generated in the Animal System. — Water in large quantities 
is as necessary to plants as to animals ; but it serves an important pur- 
pose in the vegetable world, which it does not, or but to a small de- 
gree, in the animal kingdom. Plants decompose it, and use its ele- 
ments to form their peculiar compounds. The animal possesses this 
power in but a limited way, if at all ; on the contrary, it is one of it* 
leading oflices to combine the elements which the plant separated, 
and thus ^ro^Mce water. Hydrogen and oxygen combiue continually 
in the combustion of food, so that in reality, a considerably larger 
quantity of water is excreted from the system, than was introduced 
into it in that form. 

702. Inflaence of Water upon Digestion. — We have referred to the 
remarkable solvent powers of water (367). If we could look into the 
living organism, we should see that its whole scheme is but an illus- 
tration of it. Blood, juice of flesh, bUe, gastric and pancreatic fluid, 
saliva, mucus, tears, perspiration, and all other peculiar liquids of the 
body, are simply water, containing various substances in solution. In- 
deed, the final result of the whole digestive process is to liquefy the 
aliments, or dissolve them in water. The effect of taking liquids is of 
course to dilute the bodily fluids, just in proportion to the amount 



376 PHYSIOLOGICAL EFFECTS OF FOOD. 

taken. The first efiect will be a dilution of the gastric jnice of the 
stomach, but the Avater is rapidly absorbed into the blood, which is 
thus made thinner. It has been taught that the effect of swallowing 
much liquid during meals is to lower the digestive power by diluting 
and weakening the gastric juice. This is, hoAvever, denied by high 
authority. We know that excessive eating is usually accompanied by 
a copious use of liquids, so that it is easy to commit the mistake of 
charging the evils of over-eating to the account of over-drinking. In 
such cases abstinence from drinks may be commended as a means 
of enforcing moderate eating. Dr. Chambees, of London, asserts 
that, " A moderate meal is certainly easier digested when diluents 
are taken with it." Again he remarks, " Aqueous fluids in large quan- 
tities during meals, burden the stomach with an extra bulk of matter, 
and, thei'efore, often cause pain and discomfort, but that they retard 
digestion I do not believe. Indeed, among the sufferers from gastric 
derangements of all kinds, cases frequently occur of those who cannot 
digest at all without a much more fluid diet than is usual among heal- 
thy persons." 

703. Water inflncnces cliange of Tissue. — Beyond digestion is meta- 
morphosis of structure, and this is influenced by the amount of watei 
drank. Eecent careful experiments by Dr. Bocker, performed upon 
himself, show that the use of any quantity of water above the actual 
demand of thirst, and the essential wants of the system, increase the 
transformations of the solid parts of the body. He first ascertained 
what quantity of food and drink was just sufficient to satisfy his appe- 
tite and cover the losses of the system. He then found that by con- 
tinuing the same quantity of food, and increasing the proportion of 
water, the weight of the body constantly diminished. The excess 
of water increased the waste, so that the same food Avould no longei 
restore it — the balance inclined on the destructive side. Neither thi 
pulse nor respiration were affected, but there was more languor aftei 
exercise, while the sensation of hunger kept pace with the increased 
metamorphosis of matter. 

704. Tea and Coffee. — These are taken in the form of infusions, tlu 
composition and preparation of which have been described (551). 
They are allied to foods by whatever nutritive constituents they hap- 
pen to have, which are inconsiderable, and they are distinctly separa- 
ted from them by possessing certain additional qualities which do not 
pertain to nutriment. The ingredients to which tea and coffee owe 
their peculiar action are theia and cafein, tannic acid and volatile or 
empyreumatic oil. 



INTLUEJ^fCE OF SPECIAL SUBSTANCES. 3711 

705. Effects of Tea. — Though tea is so universally employed in diet, 
yet its effects upon the constitution are by no means precisely ascer- 
tained. Its tannic acid gires an astringent taste, and a constipating in- 
fluence in the intestines. It also acts as a diuretic. Thein and vola- 
tile oil of tea are its most active ingi-edients, producing, perhaps 
jointly, its characteristic effects upon the nervous system. It is 
acknowledged that tea is a brain excitant, that it influences the mind, 
and produces exhilaration and wakefulness. How it effects the men- 
tal faculties, observers have been unable to decide, judging by their 
discrepant statements. If the quantity of thein contained in an ounce 
of good tea (8 or 10 grains), be taken, unpleasant effects come on, the 
pulse becomes more frequent, the heart beats stronger, and there is 
trembling of the body. At the same time the imagination is excited, 
the thoughts wander, visions begin to be seen, and a peculiar state of 
intoxication supervenes; all these symptoms are foUowed by, and pass 
off in, a deep sleep. Dr. Bockee has made several careful sets of ex- 
periments upon his own person to determine the physiological effects 
of tea. He took exact account of the quantity of aliment ingested, of 
the substances excreted, of his own weight, and the general bodily 
sensations. His investigations lead to the conclusion, ^rs^, that tea in 
ordmary doses has no effect on the amount of carbonic acid expii-ed, 
the frequency of the respirations, or of the pulse ; second, when the 
diet is insufficient, tea limits the loss of weight thereby entailed ; 
third, when the diet is sufficient, the body is more likely to gain weight 
when tea is taken than when not ; fourth, tea diminishes the loss of 
substance in the shape of urea, lessens the solid excretions, and limits 
the loss by perspiration. It is thus claimed that this beverage is an 
enlivener of the mind, a soother of the body, and a lessener of the 
waste of the system. 

706. Inflacnce of Coffee in Digestion. — The active ingredients of cof- 
fee are cafein, which is identical in properties with thein of tea, and 
the peculiar cmpyreumatic or burnt oil produced in roasting. " By 
the presence of cmpyreumatic substances, roasted coffee acquires the 
property of checking those processes of solution and decomposition 
which are begun and kept up by ferments. We know that all cm- 
pyreumatic bodies oppose fermentation and putrefaction, and that, for 
example, smoked flesh is less digestible than that which is merely 
salted. Persons of weak or sensitive organs will perceive, if they at- 
tend to it, that a cup of strong coffee after dinner, instantly checks 
digestion ; it is only when the absorption and removal of it has been 
effected, that relief is felt. For strong digestions, which are not suf- 



378 PHYSIOLOGICAL EFFECTS OF FOOD. 

ficiently delicate reagents to detect such effects, coffee after eating 
serves from the same cause to moderate the activity of the stomach, 
exalted beyond a certain limit by wine and spices. Tea has not the 
same power of checking digestion ; on the contrary, it increases the 
peristaltic motions of the intestines, and this is sometimes shown in 
producing nausea, especially when strong tea is taken by a fasting 
person" — (Liebig.) 

707. Lehman on the inflnence of CoflTee. — We are indebted also to Pro- 
fessor Lehman for valuable experiments to ascertain the effects of cof- 
fee. He states that coffee produces two leading effects upon the gen- 
eral system, which it seems difficult to associate together, viz : height- 
ening vascular and nervous activity, and at the same time protracting 
the decomposition of the tissues. The cafein and oU both contribute 
to the same peculiar stimulant effects, by which it rouses the exhaust- 
ed system and promotes feelings of comfort and cheerfulness. He 
finds that in retarding the decompositions of the body, it is the em- 
pyreumatic oil of the beverage that chiefly acts, the cafein only pro- 
ducing this result when taken in larger than usual proportion. Excess 
of this oil causes " perspiration, diuresis, quickened motion of the 
bowels, and augmented activity of understanding, which may indeed, 
by an increase of doses end in irregular trains of thought, congestions, 
restlessness, and incapacity for sleep ; and that excess of cafein pro- 
duces increased action of the heart, rigors, derangement of the renal 
organs, headache, a peculiar inebriation, and delirium." 

708. Chocolate is allied to tea and coffee by its nitrogenous princi- 
ple (theobromin), but the effect of this substance seems to be less 
marked than in the other cases, and has not been clearly traced. li 
is more nutritive than those drinks from its larger proportion of albu- 
men and fat, but the excess of the latter substance makes it indigesti- 
ble and offensive to delicate stomachs. 

709. Alcoholic Liqnors. — The common and active principle of spirit- 
ous liquors is alcohol, obtained from sugar by fermentation. It varies 
in proportion in the different sorts from 1 to 50 or 60 per cent. 
Liquors contain various accompanying substances, traces of albumen, 
sugar, acids, volatile oils, ethers, bitter principles produced in the pro- 
cess of fermentation or distillation, or purposely added to suit the de- 
mands of taste. The scale of commercial valuation of alcoholic liquors 
is made to depend, not on the peculiar spirituous principle, which is 
cheap, but on the attending flavoring ingredients, and various sub- 
Btances which are said to modify the eftect of alcohol upon the sys- 
tem. Yet it is the alcoholic principle found in all these mixtures that 



INFLUENCE OF SPECIAL SUBSTANCES. 8 TO 

gives them life, and a common chai-acter, and groups them all together 
under the common title of intoxicating liquors. It has been insisted 
by some that alcoholic beverages are entitled to rank as food or nutri- 
ment, but the claim is inadmissible, and moreover, is not urged by the 
most discriminatiag physiologists, even those who look with favor 
upon its general use. 

710. They cannot replace Water in the System. — Water is the ap- 
pointed solvent within the living body. Aided by acids, alkalies, salts, 
it brings the various solids into the required condition of solution. 
Bui alcohol cannot replace water in this duty. Its solvent powers are 
not the same as those of water. What alcohol dissolves, water may 
not, and the reverse. Alcohol mixed with water may deprive it of 
its solvent powers in particular cases. This is jwecisely what is done 
when alcoholic liquids are taken into the stomach. They coagulate, 
and precipitate the pepsin dissolved in the watery gastric juice, and if 
not quickly absorbed by the stomach into the blood, they would in this 
way effectually stop digestion. Their action while within the stomach 
is to disturb and arrest the digestive process. 

711. They cannot nourish Tissue. — Alcohol contains no nitrogen; it 
cannot, therefore, be transformed into tissue, nor take part in meta- 
morphic changes. Its composition forbids the possibility of any such 
effect, and nobody acquainted with the rudiments of physiology 
claims it. 

712. Their relation to Animal Heat. — The assumption that alcohol 
is a respii'atory aliment is plausible at the first blush, but conceding the 
utmost demand — that it undergoes combustion in the body — it is en- 
tirely impossible to sustain the doctrine. True, alcohol gives rise to 
heat in the system, but so do other agents, whose claim to the charac- 
ter of foods would be on their face preposterous. The question is, do 
these liquors produce heat in the manner of foods, or in some unnatu- 
ral and injurious way. By reference to Liebig's scale of respirants 
(743), it will be seen that the strongest spirits drank are inferior, 
pound for pound, to starch and sugar, and not nearly half so valuable 
as oily substances for a heat generator. Yet they act in such a rapid, 
flashy way, as to produce preternatural excitement and irritation in the 
system. In sustained calorific effect, they ai'e not to be compared with 
the aliments provided by nature, as is emphatically attested by the 
concurrent experience of Arctic voyagers exposed to the utmost se- 
verities of cold. 

713. Dr. Boeker's Obseryations. — This gentleman tested the effects of 
alcohol in small quantities upon his own person, in a course of skilfully 



380 PHYSIOLOGICAL EFFECTS OF FOOD. 

conducted experiments. lie found that this substance diminishes both 
the solid and liquid constituents of excretion by the kidneys, that it does 
not increase perspiration, that it diminishes the quantity of carbonic 
acid exhaled by the lungs, while the quantity of water thrown off by 
these organs remained unchanged, or, if any thing, was slightly re- 
duced. The general action, therefore, was that of an arrester of the 
bodily changes. As carbonic acid is hindered from being freely ex- 
creted, it accumulates in the blood in poisonous quantities, and thus 
contributes to the effects of intoxication. 

714. Is its nse Physiologically Economical, — The apologists for the 
general and moderate use of alcoholic beverages, cannot agree among 
themselves upon any philosophy to suit the case. Dr. Moleshott 
says, "Alcohol may be considered a savings-box of the tissues. He 
who eats little and drinks a moderate quantity of spirits, retains as 
much in the blood and tissues as a person who eats proportionally 
more, without drinking any beer, wine, or spirits. Clearly, then, it is 
hard to rob the laborer, who in the sweat of his brow eats but a slen- 
der meal, of a means by which his deficient food is made to last him a 
longer time." Upon which Dr. Chambers justly remarks, " This is 
going rather too far. When alcohol limits the consumption of tissue, 
and so the requirements of the system, while at the same time a man 
goes on working, it is right to inquii'e, whence comes his new strength ? 
It is supplied by something which is not decomposition of tissue ; by 
what, then ? " Dr. Liebig points out the consequences of that pecu- 
liar economy by which the laboring man saves his tissue and the food 
necessary to repair it by the use of liquors. "Spirits, by their action 
on the nerves, enable the laborer to make up for deficient power (from 
insufficient food), at tlie expense of his hody, to consume to-day that 
quantity which ought naturally to have been employed a day later. 
He draws, so to speak, a bUl on his health which must be always re- 
newed, because, for want of means, he cannot take it up ; he con- 
sumes his capital instead of his interest, and the result is the inevita- 
ble hanhruj^tcy of his iody.''^ 

715. Stimulating effect of the Beverages. — They produce general stim- 
ulation ; the heart's action is increased, the circulation quickened, the 
secretions augmented, the system glows with unusual warmth, and 
tlicre is a general heightening of the functions. Organs, usually below 
par from debility, are brougnt up to the normal tone, while those 
which are strong and healthy are raised above it. Thus the stomach, 
if feeble, for example, from deficient gastric secretion, may be »ided 
to pour out a more copious solvent, which promotes digestion, or if it 



INFLUliNCE OE SPECIAL SUBSTANCES 381 

be in full health, it may thus be made to digest more than tlie body 
requires. The life of the system is exalted above its standard, which 
takes place, not by conferring additional vitality, but by plying the 
nervous system with a fiery irritant, which provokes the vital func- 
tions to a higher rate of action. This is the secret of the fatal fascina- 
tion of alcohol, and the source of its evil. The excitement it produces 
is transcient, and is followed by a corresponding depression and drag- 
ging of all the bodily movements. It enables us to live at an acceler- 
ated speed to-day, but it is only by plundering to-morrow. By its 
means we crowd into a short period of intense exhilaration, the feel- 
ings, emotions, thoughts, and experiences, which the Author of ocj- 
nature designed should be distributed more equally through the pass- 
ing time. We cannot doubt that God has graduated the flow of these 
life-currents, in accordance with the profoundest harmonies of being, 
and the highest results of beneficence. By habitually resorting to 
this potent stimulant, man violates the Providential Order of his con- 
stitution, loses the voluntary regulation and control of his conduct, in- 
augurates the reign of appetite and passion, and reaps the penal con- 
sequences in multiform sufiering and sorrow, — for nature always 
vindicates herself at last.* 

716. Eflfects of Milk. — This is the food prepared by nature for the 
complete nourishment of the infant. It is easily digestible, but con- 
stipating. There is a difference, however, in different kinds of milk. 
Cow's milk is richer in butter, or oil, than human milk, or asses' milk, 
and for this reason often disagrees with delicate stomachs. By slcim- 
ming, however, cow's milk is made to approach human milk in quality. 
It still, however, contains nearly all the cheese, the sugar of milk, the 
salts, and some butter. It is therefore scarcely less nutritious than 
new milk, but from its loss of butter is less fattening, and has a lower 
power of sustaining, through respiration, the temperature of the body. 
Physicians order milk when they are desirous of affording stimulus 
or excitement. It is also recommended as a good diet for children, 
especially in scrofulous complaints. 

717. Properties and elTeets of Soaps. — The soluble extract of various 
animal an'd vegetable substances, obtained by boiling or steeping, forms 

* " When, by habit, the stimulant has become a necessity, an enervating relaxation in- 
fallibly follows, as sometimes mournfully illustrated by less prudent literary men. The 
stimulant ceases to excite — the debilitated organs have already been indebted to it for 
all the activity it can give. In this case the victim continues to seek his refuge, untli 
dangerous diseases of the stomach cripple the digestive powers; with the decay of the 
digestive organs, the formation of blood and nutrition are disturbed; and with the di- 
gestion vanish clearness of thought, acuteness of the senses, and the elasticity of tho 
muscles." — (Moleshott.) 



882 PHYSIOLOGICAL EFFECTS OF FOOD. 

soups. They are made from a great number of materials, and theit 
effects, of course, depend upon the substances they contain. The infu- 
sion of meat, which has been described (471), is easily digestible, 
nourishing, and well adapted to restore the exhausted strength of in- 
valids. The substance which has played the most important part in 
soups, is gelatin., the glue-principle obtained from bones, tendons, car- 
tilages, and membranes. It is this element in soup, procured by long 
boiling of animal substances, which causes it to coagulate and thicken 
(gelatinize) in cooling, and thus conveys to the uninstructed, the im- 
pression of strength and richness. Gelatin is the principle of animal 
jellies — calves' feet, blanc-mange, &c. It is an exclusive animal pro- 
duct, and never found in plants, — pectin being the vegetable jelly 
principle. Gelatin is a nitrogenous compound, but not of the protein 
type. It is regarded as a product of the partial decomposition of al- 
buminous bodies in the system, but is not capable of replacing them 
when taken as aliment. It is questioned, indeed, if gelatin, taken as 
such in food, is even capable of nourishing the gelatinous tissues. It 
is digestible in the stomach along with other nitrogenous matters, and 
finally contributes slightly, by its destruction to bodily warmth, thus 
ranking as a respirant of low power. But even this small duty is not 
performed without detriment, for while the true respirants burn com- 
pletely away, gelatin loads the blood with its incombustible and nox- 
ious residues. The French attempted to feed the inmates of their hos- 
pitals on gelatinous extract of bones; murmurs arose, and a commis- 
sion was appointed, with Magendie at its head, to investigate the 
matter ; the conclusion of which was, that giving the poor gelatin, was 
just equivalent to giving them nothing at all. The use of gelatin as a 
nutritive or invigorating substance may be regarded as given iip. The 
utmost claim now put forth for it is, that, mixed with other food, it 
makes it go further ; " but at the same time we must be careful that 
it is not used in excess, as it is apt not only to weaken the individual 
by its insufficiency as an article of diet, but causes also diarrhoea, 
whether by acting as a foreign body, or by some spontaneous decora- 
position. Hence the unwholesomeness, to healthy stomachs, of dishes 
containing a great quantity of gelatin, such as mock-turtle soup, calves' 
foot jelly, &c. At the same time, to invalids they often fulfil very 
inportant indications. In the first place they dilute nutritious matter, 
so as to render it capable of being absorbed ; then again perhaps they 
line the irritable membranes with a slimy coat, and it is not impossi- 
ble that in some cases they are beneficial because not nutritious, con- 
stituting, in fact, an agreeable mode of abstaining from food." 



INFLUENCE OF SPECIAL SUBSTANCES 883 

C— Solid Aliments. 

VIS. Starch, as we have seen, consists of hard, highly organized 
grains, enclosed in a firm envelope, so that in the raw state they defy 
the action of the digestive organs. Thorough cooking of starch, to 
break its grains, is therefore indispensable. We remember that the 
digestion of starch, altered by culinary heat, begins in the mouth by 
intermixture with saliva. Its changes in the stomach depend upon 
such previous intermixture. This explains why it is that those in 
whom the action of the salivary glands has been impaired (as tobacco 
smokers, often), complain that starchy food lays like a weight on the 
stomach. Starch prepared in the form of slops for invalids, as arrow- 
root, sago, &c., is apt to be swallowed without provoking the salivary 
flow, which prevents its prompt change ; hence starchy matter in the 
solid form, as bread or potatoes, which require mastication, is likely 
to be best digested. Starch is mainly changed in the system to sugar, 
perhaps some of it becomes dextrine and lactic acid. 

719. Sngar. — Of the behavior of this substance in the system, we 
know very little positively. A portion of it is absorbed through the 
veins into the circulation, and then burned away for the production 
of beat. But it contributes to other objects also. Another part is 
turned into lactic acid, which may assist stomach digestion, and serve 
other important uses. Physiologists are now agreed that sugar is ca- 
pable of conversion into fat in the body. To effect this change, it is 
only necessary to remove its oxygen, the remaining hydrogen and car- 
bon furnishing the constituents of oil. A deficiency of oxygen in the 
system is a necessary condition of the accumulation of fat, as an ex- 
cess of this agent would consume the elements, and thus prevent their 
deposition. Sugar is of an acid nature, and combines Avith lime and 
the alkalies. There is an old opinion, that sugar, when eaten freely, 
attacks the teeth, corrupting them, and spoiling their color ; and re- 
cent French experiments are quoted confirming this view. Dr. 
Pkreiea declares the opinion totally unfounded, saying that no peo- 
ple on earth have finer teeth than the negroes of Jamaica, who per- 
haps use sugar most liberally. " It is probable that this erroneous no- 
tion has been propagated by frugal housewives, in order to deter chil- 
dren from indulging in an expensive luxur3% Their fondness for sac- 
charine substances may be regarded as a natural instinct ; since nature, 
by placing it in milk, evidently intended it to form part of tlicir nour- 
ishment during the first period of their existence. Instead, therefore, 
of repressing this appetite for sugar, it ought rather to be gratified in 
moderation. 



384: PHYSIOLOGICAL EFFECTS OF FOOD. 

Y20. Gnm, in composition, resembles sugar and starch, and, there- 
fore, would seem to be devoted in the system to the same final pur- 
pose — the production of heat ; but there is no evidence that it is 
absorbed into the blood, nor indeed satisfactory proof that it accom- 
plishes any alimentary purpose in the system. 

721. Supply of Oily Substances. — These are furnished to the system 
mingled by nature Avith nearly all the food we take. Milk contains 
three or four per cent, of it, wheat about one per cent., rye I'To, corn 
8 or 9, ordinary meats abound in it, while in butter, gravies, and fat 
meat, we have it concentrated and almost pure. The roots, as potatoes, 
beets, &c., contain the smallest proportion of it. The system is thus 
largely furnished with fat, ready prepared ; and moreover, when its 
supply is deficient, it has the power of producing it out of other ali- 
mentary principles, sugar, starch, and perhaps even nitrogenous sub- 
stances. The physiological services rendered by the fats are manifold 
and most important. In digestion and absorption, they undergo little 
or no change. We may consider their uses under a twofold aspect ; 
first, when laid up in the body, in a passive state ; and, second, as par- 
ticipating in the active changes of the system. 

722. The accumulated Fat of the Body. — The necessity of some sub- 
stance adapted to fill and occupy the interspaces that must occur be- 
tween bones, muscles, and vessels, is obvious. There is hence extended 
across these vacancies a fine tissue of cells filled with fat. But as un- 
impeded motion is required in all regions of the system, the matter 
built into these openings and fissures to connect the working parts 
must be of a nature to facilitate movement. The lubricating, anti- 
friction properties of the oils answer this requirement perfectly ; and 
this effect becomes the more apparent when we consider that the oily 
matter of the living body is kept by its heat, either entirely fluid, or 
nearly so. Masses of fat tissue are interposed among the muscular 
bundles of the heart to promote the ease, freedom and regularity ol 
their movements. The eye, with its retinue of muscles and nerves, is 
bedded in it ; it fills up the interstices of the intestinal cavity, to aid 
the peristaltic motion of the bowels ; layers of it are placed on the 
soles of the feet and between the bones of the joints, where it serves 
similar purposes — that of pads and cushions to break the eflFect of 
shocks, and the mechanical violence to which the body is constantly 
liable. Besides, deposited in the layer of cellular tissue, under the 
skin, it relieves abrupt inequalities of the surface, and rounds the out- 
line into curves of grace and beauty, as we notice most conspicuously 
in women and children. " The fat which smooths the bony corners 



INTLUENCE OF SPECIAL SUBSTANCES. 385 

and angles, and the narrow muscles of the foce, is the cosmetic em- 
ployed by nature to stamp the human countenance with the incom- 
parable impress which exalts it far above all the lower animals." Fat 
in a fluid state is also a very had conductor of heat^ so that the layer 
of it which nature provides under the skin answers an important pur- 
pose in protecting the body from the effects of extreme heat and cold, 
and sudden changes of temperature. Finally, in the course of our 
experience upon this water-drenched planet, it is often desirable that 
we should be able to swim, and this is only made possible by the 
extreme lightness of the fatty parts of the body. Were the fat con- 
tained in our systems as heavy as water, swimming would be imprac- 
ticable ; besides entailing upon the muscles the increased labor of 
moving the more weighty limbs and body under ordinary circum- 
stances. 

723. Behavior of Fats in the Stomach. — We have seen that fats are 
not digested in the stomach, but are reduced to a fine state of emulsion 
in the intestines, so as to be capable of absorption. But it has been 
found that their presence is essential to stomach digestion. Lehman 
ascertained "that a. certain, though small quantity of fat, was indis- 
pensable to the solution of nitrogenous articles of food during the 
process of gastric digestion." Elsassee observed in experiments on 
artifical digestion, that the solution of articles used as food is consider- 
ably accelerated by means of fat. It has been found in the case of 
dogs with artificial openings in their stomachs, that fiesh which had 
been designedly deprived of fat laid longer in the stomach, and there- 
fore required a longer period for its change than the same substances 
when mixed or impregnated with a little fat. Yet on the other hand 
excess of fat exerts an injurious action, especially in persons of weak 
digestion. Fat in small amount is thus necessary to digestion ; in the 
considerable proportion which the system requires, it ought not to 
derange the gastric apparatus ; but that it is actually a powerful dis- 
turber of digestion, in very numerous cases, is well understood. It ia 
probable that those principles which are designed to bo dissolved in 
the stomach, may be so enclosed and pervaded with fat as to cut off 
the access of the solvent juice, and thus greatly hinder solution. Tho 
way in which fat is distributed among the muscular fibres of meat, for 
example, is one thing that makes it moi-e or less easily soluble by 
stomachs deficient in gastric juice. " Miftton owes its good character 
for digestibility to the little fat there is among its close-grained fibres, 
while the flesh of the ox is infiltrated with oleaginous matter through- 
out. The oil envelops the fibres when in the stomach, prevents their 
17 



386 PHYSIOLOGICAL EFFECTS OF FOOD. 

being permeated by the gastric secretion, and so renders beef indiges- 
tible to all but robust persons. The absence of fat in fish, and in 
poultry, is one great cause of their easy digestibility in the stomach, 
though their ultimate fibre is less easily soluble than that of red meat. 
Meat or fish fried or otherwise dressed with grease is thereby ren- 
dered less digestible to weak stomachs, though to those whose gastric 
juice is sufficiently plentiful to wash away the oily envelope and pene- 
trate the muscidar fibre, it is wholesome. — (Cuambees.) Even the 
healthy stomach often recoils at certain combinations of fat, starch 
and gluten, as in the instance of the oily meats of nuts, filberts, 
almonds, walnuts, &c. 

724. Cooking inflaences the Digestibility of Fats. — The effect of cook- 
ing upon fatty substances is generally to render them less agreeable to 
the stomach, especially if the organ be weak. When speaking of 
butter, we noticed the complex composition of fats and their 
liability to be decomposed into various offensive substances. Heat 
effects these changes rapidly, and to an extent proportional to its in- 
tensity. In some, as butter, the bare act of melting produces an un- 
favorable alteration, which the morbidly delicate stomach detects. In 
frying, the temperature runs high, tending to decomposition and the 
i^z-oduction of various acrid and irritant fatty acids. Fatty matters 
thus changed, or even predisposed to change, are liable to become 
rancid by the fermenting action of the stomach, producing heartburn 
and nausea. This explains why cakes are less healthy and digestible 
than bread. The Targe proportion of butter, cream, and eggs, (the 
yolks being rich in oil,) which are usually contained in cakes, and the 
changes they undergo at the high heat of baking, impairs their diges- 
tibility. Dr. Pebeiea remarks : " Fixed oil or fat is more difficult of 
digestion, and more obnoxious to the stomach, than any other ali- 
mentary principle. Indeed, in some more or less obvious or concealed 
form, I believe it will be found the offending ingredient in nine-tenths 
of the dishes which disturb weak stomachs. Many dyspeptics, who 
have most religiously avoided the use of oil or fat in its obvious or 
ordinary state, (as fat meat, marrow, butter, and oU,) unwittingly em- 
ploy it in some more concealed form, as yolk of eggs, livers of animals, 
rich cheese, fried dishes, buttered toasts, suet puddings, &c." Dr. 
Chambers says : " Fatty food can be taken without pain by gastric 
iuvalids, very closely in proportion as it is fresh, and without rancidity. 
New made butter often agrees, when the empyreumatic. fat in baked 
meat makes it utterly indigestible. If there is much emaciation, it is 
right to try several forms of oleaginous food in each case, to see if one 



INFLUENCE OF SPECIAL SUBSTANCES. 387 

cannot be found capable of supplying nutriment to the failing adipose 
tissue." 

725. Relation of the Fats to Nutrition. — The fats are ranked as respi- 
ratory aliments, but it would be a great mistake to suppose that after 
absorption from the intestinal passage into the blood they are simply 
burned away for heat ; before their destruction they serve other and 
capital uses in the body. Fat is an essential constituent of the brain 
and nervous system ; it is thus one of the prime material substances 
destined to establish communication between mind and matter. It 
has also been lately maintained that fatty substances have an essential 
share in the tissue-making process. They do not furnish the material, 
and we do not know how they act ; but it is agreed that their pres- 
ence is necessary to the formation of cells and the growth of the 
bodily structure. Thus, in point of fact, oleaginous substances, though 
at the head of respiratory aliments, are indispensable to nutrition. 

726. Oleaginous Diet and Consumption. — Masses of crude unorganized 
matter containing coagulated albumen and half-formed cells, and 
called tubercles, are sometimes found in the lungs, producing tubercular 
consumption. The immediate cause of the disease is an abortive or 
perverted nutrition, tubercle being produced instead of true tissue. 
The seeds of consumption are most generally sown in the system in 
youth, when there is a double demand upon nutrition, for current 
waste and steady growth. There is, however, sufficient nitrogenous 
matter present to nourish the structures ; some other condition must 
therefore be wanting. It has been lately maintained that the faulty 
nutrition which results in tubercle, is caused by a deficiency of oily 
substances, and therefore such of these bodies as are easiest digested 
and absorbed have been indicated as remedies. Cod Liver Oil has 
come into use for this purpose. Dr. Hughes Bennett, who first ia- 
troduced this oil to the notice of the English and American public, 
states that butchers, cooks, oilmen, tanners, and others who are con- 
stantly coming in contact with fatty matter, are less liable than others 
to tubercular disease ; and Dr. Simpson has observed that children and 
young persons employed in wool factories, where large quanties of oil 
are daily used, are generally exempt from scrofula and pulmonary con- 
sumption. These facts would indicate that even absorption of fatty 
matter through the skin may powerfully influence nutrition. Dr. 
Bennett says that, to prevent consumption during youth, indulgence 
in indigestible articles of food should be avoided, especially pastry, 
unripe fruit, salted provisions, and acid drinks, while the habit of 
eating a certain quantity of fat should be encouraged, and, if neceS' 



388 PHYSIOLOGICAL EFFECTS OF FOOD. 

sary, rendered imperative. Dr. Carpenter observes : There is a strong 
tendency, and increasing reason to believe that a deficiency of ole- 
aginous matter, in a state fit for appropriation by tlie nutritive 
processes, is a fertile source of diseased action, especially that of a 
tuberculous character ; and that the habitual use of it in larger pro- 
portion would operate favorably in the prevention of such maladies, 
as cod liver oil unquestionably does in their cure. A most remai'k- 
able example of this is presented in the population of Ireland, which, 
notwithstanding the concurrence of every one of the circumstances 
usually considered favorable to the scrofulous condition, enjoys a 
most remarkable immunity from it, without any other assignable 
cause than the peculiarly oleaginous character of the diet usually em- 
ployed. Dr. Hooker, in a report on the diet of the sick, says : 1st. 
Of all persons between the ages of 15 and 22 years, more than one- 
fifth eat no fat meat ; 2d. That of persons at the age of 45, all except- 
ing less than one in fifty, habitually use fat meat ; 3d. Of those who 
have abstained, a few acquire an appetite for it and live to a good old 
age, while the great proportion die of consumption before 45 ; 4th. 
Of persons dying of consumption between the ages of 15 and 45, 
nine-tenths at least have never used fat meat. 

727. EflTects of Endue Proportions of Alimentary Principles. — The di- 
gestion and final use of the nitrogenous principles have been explained. 
"When taken in too great quantity, they charge the system with im- 
perfectly assimilated compounds and wrongly-changed products of de- 
composition, which are not promptly expelled, and which produce a 
gouty state of the constitution, besides influencing the course of other 
diseases. The excess of oily substances in the food tends to increase 
the proportion of fat in the body. If more is taken than can be stored 
up, or consumed by oxidation, and thrown from the skin and lungs, 
the burden of disposing of it falls upon the liver, the blood becomes 
charged with the elements of bile, and a Mlloxis condition of the sys- 
tem results. The rheumatic state of the body, like the gouty, is sup- 
posed to be connected with mal-assimilation ; but rather with a de- 
ficiency of albumen and an excess of lactic acid, derived from a rich, 
starchy, and saccharine diet. A deficiency of oleaginous substances 
tends, as we have just seen, to produce the scrofulous state, and alack 
of fruits and fresh vegetables engenders the scoriutic condition of body, 
or scurvy. 

728. Flesh Meats. — Having considered the action of tbe constitu- 
ents of flesh, little needs to be added here concerning their combined 
eflect. The loss the fibre of meat has been dried or altered by cook- 



INFLUENCE OP SPECIAL SUBSTANCES. 389 

ing, the more juicy and abounding in soluble albumen, and the less its 
fat has been changed from the condition of perfect freshness, either 
by heat or other causes, the more digestible it is. The flesh of young 
animals contains less fibrin than that of old ones, but more soluble al- 
bumen and gelatin, and is hence more tender. This preponderance of 
gelatin explains why the broth of veal and lamb coagulates sooner in 
cooling than that of beef and mutton. Albumen is usually considered 
the most digestible form of nitrogenous matter. But as the acids of 
the stomach coagulate it before digestion, it does not appear that liquid 
albumen is more digestible than that partially coagulated. Eggs 
boiled, not too hard, are therefore quite as digestible as if taken raw. 

Y29. Preparations of Flonr. — Of the products of grain and flour 
which we get in multifarious shapes, baked and boiled, it may be 
said, their digestibility depends first and mainly upon their condition 
as respects lightness or heaviness. The porous and spongy state, as in 
good bread, is most favorable to the penetration and action of the di- 
gestive juices, while glutinous masses in a dense compact condition, 
especially if charged with fat, are the torment of weak stomachs, re- 
quiring the strongest digestive powers for their reduction. It is very 
diflicult to preserve the loose and open texture of flour-paste, or 
dough in boiling, and hence pastry, dumplings, &c., are very rarely 
light or digestible. Dr. Paris remarks, " All pastry is an abomina- 
tion. I verily believe that one-half at least of the cases of indiges- 
tion which occur after dinner-parties, may be traced to this cause. 
The most digestible pudding is that made with bread or biscuit and 
boiled flour ; latter puddings are not so easily digested, and suet pud- 
ding is to be considered the most mischievous to invalids in the whole 
catalogue." Dr. Lee observes, " It is doubtful whether there is any 
way of boiling wheat dough so as to render it fit for food ; it will al- 
ways be crude, and heavy, and impermeable to the gastric juice. Our 
best puddings are those made of rice, bread, sago, or Indian meal 
baked. Boiled Indian puddings are not very indigestible, and are far 
preferable to those of wheat." 

730. Coarse and Fine Bread. — As respects the final or nutritive 
effects of ground grains, it makes every difference whether they be 
bolted or unbolted. "We have stated the composition of flour from the 
interior of the seed, and the whole flour, which includes the bran 
(441). The fine or bolted flour has less of the fibre-building gluten, 
and is therefore less nourishing and strengthening. The unbolted 
sorts, and even the dark-colored sorts, through wliich finely-pulver- 
ized bran is diffused, are more digestible ; the fibrous or ligneous par- 



390 rnYSIOLOGICAL EFFECTS OP FOOD. 

tides act as a kind of mechanical divisor, separating and diluting the 
highly-concentrated food, renderin<r the mass looser and more pene- 
trable to the solvent liquids, and suomitting it more gradually to the 
membranous absorbing surface. The ground grain, or woody fibre, 
mingled with the flour, together with the adhering oil, are further ser- 
viceable by promoting the action of the intestines. Bread from fine 
flour is constipating, while that from whole flour has an aperient ten- 
dency, although it is not purgative. Unquestionably, coarse bread is 
much superior to fine for maintaining the free and regulated action of 
the bowcis, and Mr. Geaham insists strongly, as the result of large ob- 
servation, that coarse bread is corrective, not only of undue consti- 
pating tendencies, but also of morbid and chronic laxity ; though at 
first it may seem to aggravate the symptoms, yet the final result is de- 
clared to be most decidedly beneficial. Besides, in the fine flour we 
miss the fuU proportion of the elements of bone and tooth nutrition, 
the essential mineral phosphates. The nourisliment of the bony parts 
must be deficient, having less volume, solidity, and strength, with a 
diet of fine bread than with the coarser varieties. "We have sacrificed 
several most important qualities, and gained only w^i^ene^s. "We trifle 
■with the first conditions of health to gratify a fancy of the eye. 

731. Beans and Peas. — The digestibility of these is much dependent 
upon their preparation. When old and hard, and cooked with their 
husks and shells, and more especially if boiled in hard water, which 
prevents the softening and solution of their nitrogenous matter, they 
are apt to be very indigestible and heating, occasioning flatulence and 
sometimes colic. When boiled in soft water, the nutritive principle 
softens, partially dissolves, and becomes more digestible if the husks 
are separated by passing through a hair sieve. Soup is, therefore, the 
best form in which dried beans and peas can be taken. 

732. Vegetables. — The healthful and indispensable influence of fresh 
vegetables in diet is undoubted. They are rich in valuable saline sub- 
stances, essential to the system, and probably act by these as antiscor- 
butics, — preventives, and remedies of scurvy. They of course vary in 
digestibility, according to the proportion of their constituents, and the 
thorough softening and decomposing eflfect of culinary heat. Most 
esculent vegetables abound in indigestible ligneous tissues, which pro- 
voke intestinal movement, and thus incline to produce aperient eftects. 
Leaves and young shoots contain organic acids ; thus, asparagus and 
the whole cabbage tribe contain acid of apples, or malic acid ; rheu- 
barb, malic and oxalic acid ; white cabbage converted into sour krout 
ferments and yields large quantities of lactic acid. These acids may 



IJfFLUENCK OF SPECIAL SUBSTANt!ES. 391 

contribute to stomach-digestion, promoting the solution of the more 
nutritive aliments. In the case of fruits, which are still richer in 
acids, this effect is more marked. 

733. Edible Roots, of which the potato ranks first, are superior in 
dietetic importance to the vegetables just referred to. Besides their 
chief constituents, water, starch, and albumen, potatoes contain malic 
acid and asparagin^ a nitrogenous substance existing also in asparagus. 
Potatoes are rich in all the mineral ingredients required by our bodies, 
and are of permanent value against scurvy ; they especially abound in 
potash. Turnips contain no soda, but little iron, and considerable 
potash. Onions have a peculiar volatile oil which is not assimilated 
or destroyed by the body, but escapes through the lungs, contaminating 
the breath. 

Y34. Fruit. — The delicious and refreshing taste of fruits is caused 
by a combination of sweets and sours, sugars and acids. The sour taste 
predominates in the green fruit, for although the quantity of acid in- 
creases as the fruit ripens, yet the sugar increases so much faster, that 
there is a gradual sweetening as the fruit matures. In ripe fruits the 
acids are enveloped in sugar, just as in stewed fruit they are in the 
vegetable jelly, produced by stewing. In stewed and prepared fruit, 
the sugar and jelly cover, or, as it were, mask the acids and salts, and 
thus check their irritating action upon the interior coating of the di- 
gestive passage. The following suggestions of Liebig concerning the 
value of apples, afford us hints of the utility of fruits generally. 
" The importance of apples as food has not hitherto been sufficiently 
estimated or understood. Besides contributing a large propertion of 
sugar, mucilage, and other nutritive compounds in the form of food, 
they contain such a fine combination of vegetable acids, exti active 
substances, and aromatic principles, with the nutritive matter, as to 
act powerfully in the capacity of refrigerants, tonics, and antiseptics, 
and when freely used, at the season of ripeness, by rural laborers and 
others, they prevent debility, strengthen digestion, correct the putre- 
factive tendencies of nitrogenous food, avert scurvy, and probably 
maintain and strengthen the power of productive labor." 

735. Seasoning Agents, or Condiments. — Substances taken in small 
quantities for the purpose of flavoring, and rendering foods palatable, 
are called condiments. Few or none, however, are merely limited to 
this effect ; they serve other purposes besides ministermg to the taste. 
Sugar, oil, acids, and common salt, have been described as aliments, 
but they are also employed as condiments. 

736. Cheese. — We may regard cheese as an aliment when consider- 



392 PHYSIOLOGICAL EFFECTS OF FOOD. 

ing it as composed simply of casein and fat, to be digested and ab- 
eorbed. Thus regarded, it is a higlily concentrated food, difHcult of 
digestion. But it is also used in small quantities in a condimentary 
way, and may thus possess active properties in relation to digestion. 
Old, changed, and mouldy cheese has long had the reputation of being 
a digester, that is, of assisting in some manner the action of the stom- 
ach, and for this purpose it is often taken in trifling quantities after a 
meal. Being in a state of decomposition, it is capable, when mingled 
with the contents of the stomach, of exciting fermentation, and thus 
of assisting the process. Of course, if the cheese be fresh, or not in 
the mouldy, putrefactive condition, it can be expected to produce no 
such result. 

737. Vinegar, in small quantities, by augmenting the acidity of the 
stomach, may help digestion, assisting the solution of albumen, gluten, 
and fibrin. It does not, however, dissolve the legumin of peas and 
beans, but rather precipitates it from solution. An idea has prevailed 
that the free use of vinegar promotes leanness. However the fact may 
be, the experiment of reducing corpulence in this way is fraught with 
the danger of establishing deeply-rooted disease (775). 

738. Spices, &c. — A class of substances rich in punge nt oils, — horse- 
radish, mustard, pepper, cloves, and various spices, ai'e in extensive 
request as condiments. These oils produce a heating, irritating eifect 
upon the organs of taste, and the stomach ; upon entering the blood, 
they increase the circulation, and give rise to stimulation. " Con- 
diments, particularly those of the spicy kind, are not essential to the 
process of digestion, in a healthy state of the system. They atford no 
nutrition. Though they may assist the action of a debilitated stom- 
ach for a time, their continual use never fails to produce a weakness 
of that organ. Tliey aifect it as alcohol or other stimulants do — the 
present relief afforded is at the expense of future suffering. Salt and 
vinegar are exceptions, and are not obnoxious to this charge, when 
used in moderation." — (Dr. Beaumont.) 

10. NuTEiTivE Value of Foods. 

739. Limitation of the Nutritive Powers. — It is to be expected that 
substances diifering so widely as those which constitute food — sub- 
stances of such various composition — some containing nitrogen, while 
others are free from it, some containing sulphur, others none, some an 
excess of carbon, others the reverse — must serve very different pur- 
poses in tl e economy. Each has its special work to do, while their 
duties are not interchangeable. A certain degree of variety is thus 



ITS NUTRITIVE VALUE. 393 

the fundamental requirement of the system ; and accordingly we find 
that where nature herself has prepared the food, as in the case of 
the mother's milk for her young, it is always of a mixed nature, 
embracing alimentary principles of very different composition. We 
have no shadow of evidence that the living body possesses the power 
of converting one element into another ; it cannot transmute hydrogen 
into nitrogen, or carbon into phosphorus ; if it lack an element, it 
must suffer the inconvenience of deficiency. As regards the conver- 
sion of one compound into another, the system has a limited faculty 
of this kind in a certain direction ; it can effect some changes, as Ave 
have seen ; it cannot effect others. It can destroy compounds by a 
progressive series of changes, each descending step being a new sub- 
stance, but it cannot work upward in a formative direction, — that is 
the ofiice of plants. The materials necessary to form a compound may 
be present in the body without any power whatever to produce it. 
The dissevered constituents of used-up tissue, exist in the blood, but 
it is entirely incapable of reconverting them into tissue, Nor has the 
body the power of transmuting the respiratory group of aliments into 
the albuminous, or of enabling the former to replace the latter, in the 
exigencies of the animal economy. It cannot make starch do the 
work of gluten. " That none of the non-nitrogenous substances can be 
made capable, by metamorphosis or combination within the animal 
body of taking the place of the nitrogenous or plastic compounds, may 
now be regarded as one of the most certain, facts in physiology ; the 
concurrent evidence of experiment and observation tending to the 
conclusion, that in plants alone can any production of nitrogenous 
compounds take place. If animals be fed exclusively on saccharine or 
oleaginous substances of any kind, or in any combination whatever, 
they speedily perish with symptoms of starvation." — (Dr. CAEPE^'TEE.) 
As the system has no mysterious energy to change icliat it will and as 
it will, its action being absolutely limited, it follows that its nutritive 
supplies must be adapted to its wants. . 

740. ML\ed Diet Indispensable. — Our diet thus requires to be of a 
mixed nature, comprehending such a variety of materials as to supply 
the whole rauge of bodily wants, and moreover, should be varied with 
the varying circumstances of growth, bodily and mental exercise, tem- 
perature, and numerous changing requirements of the system. Hence 
the impossibility of prescribing any thing like precise and invariable 
rules in reference to the quantity and proportions of alimentary sub- 
stances. We now call attention to the comparative values of nutritive 
substances, in certain important respects, as based upon composition, 

17* 



594 



PnYSIOLOGICAL EFFECTS OF FOOD. 



and experience of their effects. We shall have occasion to note both 
agreement and discordance, in many particulars, between general 
habits and the indications of science. 

741. Proportions of Solid Matter and Water. — The following scheme, 
Fig. 121, illustrates the proportion of solid matter and water contained 
in the principal articles of diet. They were dried at 212; the results 
are averages of statements by the best authorities. The length of the bars 
represent the proportion of dry solid matter in 100 parts, the remain- 
der of the hundred indicated by the scale being water. The preva- 

Fig. 121. 
PEOPOETION OF SOLID MATTER AND WATER IN FOODS. 

, 10 , 20 , 3,0 , 40 , 50 , 60 , 70 80 , 90 100 

p'TTjlT'T^^TTtTiTrtlTiTT-TTliTT^^ 

"Wheat, Peas. 

Eico, Kye, Beans, Corn. 

Wheat Bread. 

Mutton. 

Chicken. 

Lean Beef. 

Eggs. 

Veal. 

Potatoes. 

Pork. 

Cod. 

Blood. 

Trout. 

Apples. I 

Carrots. 

Beets. 

Milk. 

Oysters. 

Muskmclon. 

Cabbngo. 

Turnifis. 

Watcrmeliin. 

Cucninber.s. Bl 

The length of the bars represents upon the scale, the percentiigo proportion of solid mat- 
ter in the various articles of diet, opposite to which they are placed. 

lence of the aqueous element in diet, is thus strikingly apparent. Most 
of the articles contain 75 per cent, water ; some much more. The 
grains are driest, but in being reduced to bread tliey become more 
than half water, and even then we take additional liquids freely while 
eating it. Water is essential to food, but to make the best statement 
of its nutritive value, wo must throw this constituent out of the ao- 




ITS NUTRITIVE VALUE. 



395 



count, and regard only the dry matter. But the quantity of solid sub' 
stance left, is no guide to its nutritive effect ; potatoes and lean beef 
have the same proportion of water, but they are certainly widely apart 
in nutritive power. 

7i2. How far we can measure Nutritive Values. — A full view of the 
nutritive value of foods, requires us to take into account all their 
effects ; but we are as yet far from being prepared to do this on any 
systematic or comparative scale. The nearest approach to a state- 
ment that can be ventured, is by classifying foods in reference to the 
two great leading purposes which they serve in the system — forma- 
tion of tissue, and production of heat — the proportion of the nutritive 
to the calorifient principles. This division, although fundamentally 
true, and capable of being embodied in a valuable shape, we take with 
its qualifications ; for as has been stated, the respiratory princii^les 
contribute also to nutrition, while the albuminous may produce 
heat (66G). 

743. Different ralucs of tlie Respiratory Principles. — The albuminous 
substances are identical in composition, and have equal nutritive 
powers; whether in the form of gluten, fibrin, casein or albumen, 

RELATIVE POWEES OF THE HEAT-PEODTJCIIsrG PEINCIPLES OF FOOD. 
Fig. 122. 



Fat. 

Starch. 

Cane Sugar. 

Grape Sugar. 

fiplrlts, 50 per ct. Alcohol. 

Lean Flesh, 



The relative lengths of the bars illustrate the comparative amount of heat produced in 
the system by equal weights of the substances mentioned. 

they are replacable in nutritive effect. Not so, however, with the 
calorifient principles ; their heat-giving powers are very unequal. 
The preceding diagram (Fig. 122), exhibits the relative proportions 
of heat produced by equal weights of the substances mentioned. It 
wiU be thus seen that 10 parts of fat go as far as 24 of starch in 
generating heat. This is Liebig's estimate. He calculates the oil as 
larcli, by multiplying it by 2*4. Thus the 9 per cent, of oil in Indian 




396 PHTSIOLOGICAJL EFFECTS OF FOOD. 

corn, would be equal to adding 22 per cent, to its real amount of 
Gtarch. In this way, the nutritive and calorifient powers of foods are 
readily brought into comparison. It appears from this estimate of 
LiEBiG, that the strongest spirits are not only incomparably inferioi 
to the oils, in heat-producing power, but also rank decidedly below 
starch and sugar (712). "When we remember that alcohol is derived 
from sugar by a destructive process, in which half the saccharine sub- 
stance is lost, and that the product obtained is still below sugar on 
the heat-making scale ; it is clear, that the use of alcohol as a respira- 
tory substance, is any thing but good economy. 

744. Bad Ecouomy of an exclnsivc Meat Diet. — It is seen by the fore- 
going scale, that lean meat is the feeblest of all respirants If it is to 
be employed, not only for nutrition, but to produce heat, an enormous 
quantity of it must be consumed. As the largest alimentar} demand 
of the system is for carbon and hydrogen to support respiration, the 
nitrogenous principles being low in these elements, afford the least 
economical diet that can be adopted. Thus it has been calculated, 
that since fifteen lbs. of flesh contain no more carbon than four lbs. of 
starch, a savage with one carcass and an equal weight of starcli, 
could support life for the same length of time, during which another, 
restricted to animal food, would require five such carcasses in order to 
produce the carbon necessary for respiration. The mixture of the nitro- 
genous and non-nitrogenous compounds, (gluten and starch,) that exist 
in wheat flour, seems to be just that which is most generally useful to 
man ; and hence we see the explanation of the fact, that from very 
early ages, bread has been regarded as the ' staff of life.' 

745. Equilibrium of Values Disturbed. — When the due proportion 
demanded by our physiological welfare, is struck, between the nutri- 
tive and respiratory principles, they may be regarded as of equal 
values ; that is, they are both, in their just relative amounts, equally 
necessary, and a diminution of either produces injury. But under 
ordinary circumstances, the nitrogenous matters are most difiicult to 
obtain. They exhaust the soil most, and the tendency of cropping is 
to reduce their proportion in equal weights of alimentary products. 
They represent animal power, are more complex and highly organized, 
are less easily produced, and more destructible than the other group. 
The value of foods, therefore, under ordinary circumstances, rises and 
falls mainly in correspondence with the -proportion of these constit- 
uents. But in case of famine, or arrest of production, these conditions 
are reversed. Crops of green roots and vegetables, the immediate 
and principal sources of respiratory food, in the shape of starch, sugar, 



ITS NTTTRITTVE VALUE. 



397 



and oil, are cut off. "We fall back upon the animal world, but this is 
chiefly a grand store of nitrogenous matter, without its due proportion 
of other constituents. The balance being thus lost, respiratory food 
rises in demand and value. 

746. Proportion of Nutritive to Calorificnt Principles. — The following 
scheme represents approximately the values, nutritive and calorifient 
— building materials and fuel — of various articles of food. It must be 
received as only a general or outline expression of the facts. Different 
samples of the same food vary in composition ; an average is the best 
residt that can be obtained. 

Fio. 123. 

OOMPAKATIVE SCALE OF THE NXJTEITIVE AND EESPIRATOEY VALUES OP 

VARIOUS ARTICLES OF FOOD. 



Natritive or tissue- 
forming principles. 



*Veal. 
Hare. 
Dried Beef. 
Eggs. 
Beef. 
Beans. 
Peas. 
Fat Mutton. 
Pork. 
Cow's Milk. 
Human Milk. 
Wheat Flour. 
Eye Flour. 
White Potatoes. 
Indian Com. 
Turnips- 
Blue Potatoes. 
Kice. 
BucKwheat Flour. 

Arrow-root, sa- ( 
go, tapioca, •< 
corn-starch I 



Calorifient or heat-pro 
ducing principles. 

10 , 20 ,30 40 50 



l?0 t30 




This scheme represents, by the relative len?jth of the bars, the proportion of uitroirinmi.s Id the 
non-nitrogenous principles in each article given, the latter being all reihiccd to the value of 
starch. The upper part of the .scale represents those foods which are highest In proper nutri- 
tive power, and lowest in heat-producing effect, while the lower portion exhibits those 
which are lowest in nutritive, but highest in calorifying effect. 



♦The authorities for the above scale are as follows, In numerical order, counting from the 
.op downward: 1, 2, 5, (i, 7, S, 9, 10, 11, 12, l-., 14, IT, 18, 19 (Lrr.niG); 3, 4, IG (Prof .Ioum 



, UJ» »H7>> II *> til U . I , ^, »/, T', 1^ ", f^ A", J. 1 . Afci, 1-1, X 

ton); 20 (Prof U. D.Thompson); 15 (Authou). 



398 PHYSIOLOGICAL EFFECTS OF FOOD. 

The point to wbicli we called attention in the previous paragraph 
must not be forgotten, or the scheme will certainly mislead us. 
The calorifient principles are reduced to the expression for starch, so 
that wherever fats are involved, the respiratory equivalent appears 
higher than the quantities furnished by analysis would otherwise war- 
rant. Thus, if we take the weight of the casein of milk to represent 
its nutritive power, and the combined weights of the sugar and butter 
to represent the respiratory effect, we shall get a result diflferent from 
that in the table, 10 of nutritive, to 18 or 20 of respiratory food. 
LiEBiG says in substance, in connection with this statement, that the 
relative proportions of the nutritive constituents :ii milk, to its butter 
and milk-sugar, that of the plastic matter of flesh to its fat, and of 
the albuminous substance of grain, potatoes, peas and beans to their 
starch, are not constant. They vary in milk with the food ; fattened 
flesh contains more fat than that which is lean ; and the difference be- 
tween the two kinds of potato shows how great may be the variation 
in different varieties of the same plant. But the above may be re- 
garded as average numbers lying between the opposite extremes in 
each case. We may consider as constant the following results, 
namely, that peas, beans, and lentils contain for one part by weight of 
plastic matter, between two and three of non-nitrogenous matter 
ranked as starch ; that grains, such as wheat, rye, and oats, contain be- 
tween five and six parts, potatoes from eight to eleven parts, and rice 
and buckwheat from twelve to thirteen parts of the latter, to one of 
the former. 

V47. Nntritive Powers of Milk. — The above scheme is rich in sug- 
gestions. The starting point of all inquiries into the nutritive quali- 
ties of foods is milk. It is the only complete or typical aliment fitted 
to nourish the entire body ; the only dietetic prescription that nature 
has furnished to fill the full circle of bodily wants. The water is there 
in large proportion to supply the necessary liquids, the mineral salts, 
to build the bony framework, the casein to form the tissues, and but- 
ter and sugar to sustain the bodily warmth. Not only does it contain 
every thing the system requires, but in proportions exquisitely adapted 
to the demands of peculiar and varying conditions. It is the appointed 
diet of the infant, the chief business of which is to grow. Its diet 
must, therefore, not only be adjusted to meet its current waste, but it 
requires to be especially rich in the structure-making constituents, and 
such is the fact. The weight of the nitrogenous curd to the butter 
and sugar, is as high as 1, to 2 or 3. But see how admirably nature 
modifies tliese proportions to suit special occasions. Of all the young 



INPLUEKCE OP SPECIAL SUBSTANCES. 



399 



of the animal world, none lead so quiescent a life, or advance so slow- 
ly to maturity, as does the human infant. The young of other ani- 
mals more quickly develop, and are called upon to put forth exertion 
much earlier. Hence the mills of these animals, as for example the 
cow, is richer in the curdy, or huilding and strength-giving principle 
than human milk. 

748. Wheat resembles Milk and Blood. — "Wheat, hy universal consent, 
ranks first in nutritive value among grains. It abounds in the valua- 
ble elements which the body requires — mineral matter for bones, glu- 
ten for tissue, starch for respiration. Its deficiencies are water and 
oil ; the former we supply in converting it into bread, and the latter 
by the universal custom of using butter with it when eaten. Another 
great advantage of wheat is, that its gluten is pre-eminently of that 
quality which yields the lightest and most digestible bread. The near- 
ness of wheat flour in chemical composition to mUk and blood, is 
shown in the following analytical statement : 



Flour. 


Blood. 


Milk. 


Fibrin, 


Fibrin, 




Albumen, 


Albumen, 


Albumen, 
Casein, 


Casein, 


Casein, 


Gluten, 


Coloring matter. 




Oil and starch, 


Fats and oils. 


Butter, 


Sugar, 


Sugar, 


Milk-sugar. 


Chloride of potassium. 






Chloride of sodium, 






Phosphate of soda, 
" " lime. 


Ditto. 


Ditto. 


" " magnesia, 






" " iron, 







749. How Wheaten preparations meet the losses of the System. — Tlia 
attempt has been made to determine the daily consumption in the sys- 
tem of nutritive and respiratory matter. The problem is most difii- 
cult, and the results thus far only average and approximative. It is as- 
sumed that the waste of tissue is about a grain a minute, or 62 grains 
per hour, or somewhat more than 3 oz. per day. Poggaile states 
that the researches of the last 20 years have shown that an adult la- 
loring man consumes each day between 11 and 12 ounces of heat-pro- 
ducing principles, and about 4j ounces {dry) of nitrogenous matters, 
charged with the regeneration of the tissues ; that his nourishment is 
not complete unless it is formed of one part nitrogenous matter and 
four parts respiratory. Beneke, from an examination of the diet 
scales of various educational, invalid, and penal establishments in Lon- 
don, obtains the result that the nitrogenous should bo to the uon-nitro- 



400 PHYSIOLOGICAL EFFECTS OF FOOD. 

genous as one to five. Feeeiohs calculates that the daily consunip 
tion should be 2-17 ounces avoirdupois of nitrogenous, and 15"54 ouiicei 
of non-nitrogenous food, that is, about as one to seven. Wheat aver- 
ages, perhaps, one to five. But starch is a bulky form of respirators 
aliment, and hence it is only by the use of very considerable quanti 
ties of bread, that enough of this ingredient can bo procured to sus- 
tain the temperature. . Butter, a more concentrated heat-producer, 
comes in to assist in relieving this difficulty, and as wheat is almost 
entirely destitute of oil, it is highly probable that butter is also io- 
etinctively added to promote its digestion. 

750. Variations in Nntritive Value of Wheat. — The proportion of nu- 
tritive to respiratory principles in wheat, fluctuates much, which oi 
course, aflfects its value correspondingly. Flour containing 9 per cent., 
of gluten must give rise to very different physiological effects from 
that containing 18 per cent. The large proportion will produce th« 
blood constituents most copiously, and yield most strength. Yet, as» 
we have repeatedly stated, commercial and nutritive values, so far 
from coinciding, actually antagonize. Instead of the increasing pro • 
portion of nitrogenous compounds being any indication of the pric( 
which will be paid for wheat, it is quite the reverse. We prize anc" 
estimate flour directly in proportion to its whiteness^ which is gener- 
ally in inverse ratio to the proportion of its gluten. AVe give most fot 
the wheat that will nourish least. As the chief object of the farme^" 
is to produce an article which will command the highest marTcct price, 
he has no inducement to cultivate grains rich in albuminous com- 
pounds, but a double motive for the contrary course ; those which are 
deficient in these elements exhaust the soil less and bring most money. 
751. High Nutritive Power of co<irse Bread. — In the seventeenth 
century, Yatjbax estimated the annual consumption of a man at near- 
ly 712 pounds of wheat, a quantity which now nearly suffices for two 
men ; and by the improvements in mills, there are now gained to the 
population immense masses of nutritious matter, of the anneal value 
of many millions, which were formerly used for animals ; the bi-an 
may be far more easily replaced by other food not in the least adapted 
for the use of man. The high value of bran for food has been long 
ago pointed out. Wheat does not contain above 2 per cent, of indi- 
gestible, woody fibre, and a 'perfect mill should not yield more than 
that proportion of bran, bat practically, the best mills always sepa- 
rate, even now, from 12 to 20 per cent. (10 per cent, coarse bran, 7 
fine bran, 3 bran flour) ; and the ordinary mills produce as much as 25 
per cent, of bran, contaiuiug 00 or 70 per cent, of the most nutritious 



ITS NUTEITIVli VALUE, ♦ 401 

constituents of the flour. By baking bread with unbolted flour, the 
mass of it may be increased from one-sixth to one-fifth, and tM 
price of it lowered iy the difference heticeen the price of the Iran as 
fodder for cattle^ and that of the flour gained ly not halting it. 
The separation of the bran from the flour by bolting is a matter of 
luxury, and injurious rather than beneficial as regards the nutritive 
power of the bread — (Liebig). 

752. Aliments may be corretted by Intermixture. — Lean flesh is the 
most concentrated form of nutriment, is easily digested, and quickly 
converted again into muscle. Yet, though a most perfect nutri7nent, 
it is least fitted to meet the complete demands of the system. It is 
not a complementary food, like wheat, answering to the double re- 
quirements of the body ; its deficiency of respiratory matter makes it 
uecessary to consume with it fats and gravies, or else join it with 
those substances at the opposite extremity of the scale, rice, potatoes, 
vegetables, &c., which abound in calorifyiug matter, but are deficient 
in the nutritive. On the other hand, if we attempt to live exclusively 
on rice, potatoes, or vegetables, in order to procure sufiicient of the 
flesh-producing ingredients, we must consume an enormous bulk of 
respiratory matter, so much more than is needed, as to produce de- 
formity and disorder of the system. It is easy to see, however, by 
reference to the preceding scale, that we can make such combinations 
of dietetical articles, as shall compensate for natural deficiencies. In- 
deed, the due admixture of these diflferent principles of food, is a vital 
and immanent necessity, which, if disregarded, makes itself quickly 
felt in physiological derangement, so that man's instincts have sufficed 
to guard him in many cases against broad departures from the proper 
and healthy course. In all countries we notice dietetical adjustments 
tending to the same physiological end. In the coarsest and crudest 
diet of barbarous tribes, or- the high-wrought luxuries of the refined, 
the same instinctive cravings are ever regarded — the same purpose of 
nature is always in view. Potatoes and vegetables, with beef, mutton, 
and pork, are almost universal combinations. Beans and peas, which 
are the most highly concentrated vegetable nutriments, are associated 
with fat pork, in the well-known dislies — 'pork and beans,' 'pork 
and peas pudding,' and the extreme oiliness of ham or bacon is cor- 
rected by the highly nutritive egg {ham and eggs). So also milk and 
eggs are cooked with rice, and butter is added to bread, which is de- 
ficient in oily matter. In Ireland, where potatoes form the staple ot 
diet, and there is a deficiency of meat, they attempt a compensation 
by mingling with the potatoes boiled cabbage, which is rich in nitro- 



402 PHYSIOLOGICAL EFFECTS OF FOOD. 

genous matter, with perhaps a little meat, making a dish known as hoU 
cannon. Rice is also a staple article of food through vast regions. It ia 
very deficient as a nutriment, containing but little nitrogenous, fatty 
or saline matter. It forms an unsubstantial diet, cannot be substituted 
for meat and dry vegetables in soldiers' rations — and must always be 
combined with nitrogenous principles. Hence, whenever they can be 
obtained, milk, fish and meat are added to it ; and even with the ut- 
most procurable quantity of these substances, it is questionable wheth- 
er the natives of rice-eating countries do not owe much of their lack 
of spirit and power to defective diet. 

753. Diet required by Children. — We are reminded again, by refer- 
ence to the preceding scale of equivalents, of the ill- adaptation of rice, 
sago, arrow-root, corn-starch, &c., as diet for children. MUk, rich in 
nutrient matters, is their typical food. They require nitrogenous sub- 
stances, for the double purpose of present waste and growth. When 
fed on the substances just mentioned, which lack both nitrogenous and 
mineral substances, fat may indeed accumulate, but the frame is weak 
and rickety, from small muscles and softness of bones. Children should 
have a full supply of blood-producing foo.d — even bread contains too 
little for them — ^milk or flesh should be added. But whether fed on 
bread and milk, or meat and bread, there is apt to occur a deficiency 
of phosphate of lime, from the rapid formation of bone. But as meat, 
eggs and milk contain an excess of phosphoric acid, there being not 
enough lime to convert it all into phosphate, lime itself is a good ad- 
dition to the food of young children. It may be given in the form of 
lime-water, which the peasants of Germany give to their children with 
the best results, while the children greedily take it, guided by instinct. 
— (Gkegoey.) 

11. The Vegetarian Question. 

754. The points in Controversy. — Strenuous objection to the use of 
animal diet has been made by many, and pure vegetable products com 
mended as the best food of man. The controvei'sy has been between 
the advocates of a mixed diet, of vegetable and animal substances, on 
the one hand, and the partisans of an exclusive vegetable diet, on the 
other ; the point of contention being the dietetical fitness of animal 
'bod. The vegetarians, however, as a school, do not entirely proscribe 
animal diet. They generally admit the use of eggs, milk, butter, and 
cheese, but repudiate flesh. Mr. Graham recognizes the inconsistency 
of this course with the true vegetarian theory, and regards the use of 
those substances with disfavor, tolerating them, as it might be, imder 



THE VEGETAKIAN QUESTION. 



403 



protest. The quarrel is an old and embittered one, and has been 
made to involve all sorts of considerations. We epitomize and con- 
trast below, some of the arguments and objections which are most 
commonly started in the course of this discussion. 



ADVOCATES OF VEGETABLE DIET. 

Flesh diet involves tlio barbarous and 
unfeeling practice of destroying sentient 
life. 



ADVOCATES OF MIXED DIET. 

So does the necessary clearance of house- 
hold pests, and the insects and vermin in- 
jurious to the farm and garden. It is in- 
volved in the fundamental oixier of nature. 



In a state of primitive nature, man lived 
on vegetable products, fruits, and grains of 
the earth. 



Whatever may be true concerning the 
natural dietetic character of man, there is 
Leithcr now on earth, nor has there been 
for many centuries, any portion of the hu- 
man race, which has lived in all respects 
so perfectly in a state of nature, as to af- 
ford us an opportunity to study man's true 
natural history and dietetic habits. Ana- 
tomically, and in strict propriety, man 
must be regarded as an extinct species, 
that is, he has become so artificial in his 
dietetic habits, that they afford no evidence 
of his natural dietetic character. Man's al- 
imentary organs, if placed before us, afford 
no clear and determinate indications of his 
true dietetic character — his natural habits 
in this respect are wholly unknown, ex- 
cept as matter of history and tradition. — 
(Sylvestbe Gkahaji.) 

Vegetables afford the pure, first princi- 
ples of nature ; while animal products are 
drossy, corrupted, second-hand residues, 
from which the finer and subtler essences 
have been, as it were, exhaled and lost. 



The meat of diseased animals being eaten, 
is liable to introduce the same diseases, or 
others, into the human system. 



If so, it was because he knew no better ; 
he is a progressive being, designed to be 
civilized, and improve his condition in 
numberless ways. 

The anatomical structure of man proves 
his adaptation to a mixed diet. The her- 
bivorous animals are enabled by numerous 
and variously-formed teeth to gnaw and 
grind, and by a longer digestive canal, and 
larger salivary glands, to digest substances 
which could not be sufficiently reduced by 
the differently structured and sharper teeth 
of carnivorous animals, nor dissolved by 
their smaller salivary glands, and shorter 
intestinal canaL In the structure of man's 
stomach and intestines, teeth and jaw- 
bones, salivary glands, and muscles of mas- 
tication, we find a medium between these 
extremes, which points to a compromise in 
his diet, and indicates that he was designed 
to use both forms of food. 



There is no proof of any such difference ; 
the foundation of our being is laid in ani- 
mal nutrition ; the infant in the early stages 
of its life, is exclusively nourished by its 
mother's blood and milk. It is ordered, at 
all events, that we shall not begin our ca- 
reer as vegetarians, — a pretty distinct prov- 
idential hint t 

Diseased meat is of course unwholesome, 
dangerous, and to be rejected; but so are 
diseased grains, and damaged flour ; both 
arc liable to engender disease. 



Animal diet excites and inflames the ani- 
mal passions and propensities, favoring cru- 



But does not the carnivorous animal cat 
flesh because it is ferocious, that is, because 



404 PHYSIOLOGICAL EFFECTS OF FOOD. 

elty and ferocity of disposition, as seen in the Creator has implanted in it the instlnoti 
the carnivora; while vegetable food pro- necessary to its acquirement of the food 
duces mildness and docility of disposition for which its organization is destined; and 
(6S7). that the herb and grain eaters are without 

this savage nature, because they have no 

occasion for it, being Intended to derive their food from the produce of the soil. But 
if we admit that the habitual diet reacts upon, and tends to keep up the respective pro- 
pensities of these two classes, still there is nothing in vegetable food that necessarily 
induces mildness and docility. The ferocity of wild bulls, boars, buffalos, &c-, is well 
known. Our domesticated animals are not in their natural state, an active source of ex- 
citement and danger being removed, in the general mutilation of the males. "Wo can- 
not see the least ground for the conviction, that a man, in good average health, with no 
plethoric excitability, will be in the least changed for the better by relinquishing his slice 
of mutton and potatoes for its equivalent in wheat-flonr, or an omelet and custard-pud- 
ding. And if the effect of universal vegetarianism were to be, to reduce the character 
of all mankind to the insipidity of said omelet, and the blandness of custard-pudding, 
we, for our part, should not like the world half so well as we do now. A very excellent 
lady, who had kept a school for nearly half a century, said — ' I never liked the girls who 
were brought to me with " very good characters " from their parents; they had either 
no energy, or were very sly ; give me the naughty children ; there is something in them 
to work upon, and a promise of future activity.' The emotions and propensities are the 
sources of all action, and if these be tamed down to the vegetarian standard, we appre- 
hend that, neither will the better parts of human nature be called into energetic opera- 
tion by their own activity; nor will the worse call forth that energy for their repression, 
which is often the foundation of what is noblest in human character." — (Dr. Cakpentee.) 

Into the general question, as thus opened, we do not propose to en- 
ter ; but simply to call attention to a few chemical and physiological 
facts, which appear to have been established, and which may enable us, 
perhaps, better to comprehend the present conditions, and more strict- 
ly scientific aspects of the subject. 

755. Restricted Scope of Animal Transformations. — We recall at this 
point the statement repeatedly made, that the animal system is not to 
be viewed as capable of creating or fabricating the compound sub- 
stances which it employs in nutrition. Eecent organic chemistry 
has profoundly modified the older views of this matter. In the ab- 
sence of all accurate information, the animal system was looked upon 
as endowed with unlimited and mysterious powers of transforma- 
tion; but we now understand that those powers are definite, and 
limited within a narrow range. It is not strange that, in the absence 
of exact knowledge, but little could be discovered in common between 
herbage and dried leaves of grass consumed by an ox, and the blood 
and texture of its body. But chemistry teaches us now that the very 
identical material of blood and tissue is prepared in the vegetable, and 
that the office of the animal is chiefly limited to extracting and col- 
lecting it from its multifarious vegetable food ; it can only appropri- 
ate pre-existing compounds. 



THE VEGETARIAN QUESTION. 405 

756. Vegetable aud Animal Priaclplcs the same. — We have further seen 
that there is a remarkable identity of alimentary principles, whether 
derived from plants or animals. Vegetable and animal fats have the 
same substantial composition — are alike divisible into liquid and solid 
parts, with similar properties. And so the nitrogenous principles, 
vegetable and animal, are remarkable for their chemical similarity — 
in composition, the proportion of their elements, external properties, 
and modes and products of decomposition, vegetable albumen resem- 
bles animal albumen, and the same with casein and fibrin. The veg- 
etable principles, by simple digestive soluticm, are converted into blood 
and flesh, without decomposition, just as mineral substances may bo 
dissolved and separated, again and again, without alFecting their chem- 
ical integrity or essential properties. Wh ether we go to the vegetable 
or animal world, therefore, we get the same nutritive principles, and 
we arrive at this twofold conclusion : that, while we may procure 
every thing adequate to complete and healthful sustenance from the 
vegetable kingdom, where it is all first fabricated ; on the other hand, 
we find substantially the same principles in the animal world, with 
only modifications of form, concentration, and solubility. It would 
seem from this point of view, that we may confine ourselves without 
detriment to the former source of aliment, or resort without injury to 
the latter. 

757. Peculiar inflaence of Flesh Diet. — Yet there are important dif- 
ferences between vegetable and animal food ; in what do they con- 
sist? LiEBiG observes, "Bread and flesh, or vegetable and animal 
food act in the same way with reference to those functions, which are 
common to man and animals ; they form in the living body the same 
products. Bread contains in its composition, in the form of vegetable 
albumen and vegetable fibrin, two of the chief constituents of flesh, 
and in its incombustible constituents, the salts, which are indispensa- 
ble for blood-making, of the same quality and in the same proportion 
as flesh. But flesh contains, besides these, a number of substances 
which are entirely wanting in vegetable food ; and on these peculiar 
constituents of flesh depend certain efiects by which it is essentially 
distinguished." Reference is here made to the peculiar constituents 
of flesh-juice which have been mentioned (471). Flesh is thus a com- 
plex product, containing peculiar principles, — a result of all the diges- 
tive and preparative actions of an animal organism ; and as the 
|)urpose of food is to re-produce flesh, it is evident that no dietetical 
preparation can eflect this so perfectly, so rapidly, or with so little 
physiological labor as meat itself. Flesh is nearest to blood, and flesh 



406 PHYSIOLOGICAL EFFECTS OP FOOD. 

of all aliments is most easily converted into both. The iiigestion 
of flesh augments the proportion of fibrin in the blood, and increases 
the activity of nutrition. The heart being a tissue of muscular fibres, 
is more fully nourished ; the activity of the circulation is consequently 
increased. The 'excitation of this activity, observed after a copious 
meal of venison, is due not only to the abundance of albuminous mat- 
ters contained in the venison, but also, probably, to its proportion- 
ately large quantity of kreatin. Highly animalized diet exalts 
the density and solid constituents of the blood, and increases tlio 
number of its corpuscles or globules; but does not augment the 
proportion of its albumen. This re-enforcement of the blood by con- 
sumption of flesh, in heightening the general power of the system, of 
course, strengthens the passions and propensities. For this reason the 
term stimulating has been applied to flesh-diet. From its greater 
concentration, it is easier to over-eat "wilh animal than with vegetable 
diet. As excessive alimentation is a universal danger, the vegetarian 
is most protected, though by no means safe ; for it is very easy to 
slide into excess upon a vegetable regimen, especially if eggs, milk, 
butter, and cheese be freely used, as is very apt to be the case.* 

758. Mineral Matters Replaceable in the two Diets. — But while vegetable 
and animal food yield precisely the same organic principles to the blood, 
they do not furnish to it identical mineral constituents, as was stated 
before. The phosphoric acid which appears in the blood in com 
bination with the alkalies forming phospJiates, when animal food is 
consumed, is replaced by carbonic acid, and the carlonates when we 
change to a diet of vegetables, and fruits. Bread gives rise to phos- 
phoric acid like flesh. We called attention to this most extraordinary 
fact — that a powerful, fixed, mineral acid, and a feeble, volatile, or- 

* " The influence of diet over muscular fibre, is an important social question ; for thews 
and sinews have always ruled the world, in peace and in war, in a proportion quite equal 
to brains. Indeed, it is a question which the present writer is disposed to answer in the 
affirmative, whether nationally muscular and mental energy do not always run in couples 
and whether the first is not the cause of the second. It does not appear that any diet, so 
there be plenty of it, is incapable of fitting a man to get through his daily work in a 
fa.thion ; but the best specimens of the species in their several sorts, hunters, agricul- 
turists, or citizens, are those nations who get most flesh-meat. A collateral advantage 
of a moat diet to a nation is the difliculty of obtaining it ; for the truth, probably, is that 
the mode of procuring food has asgi'eat an influence over mind, manners, and muscles, as 
the nature of the food itself. Ho that is satisfied with what he can pick up, ready grown, 
Regenerates either into a starved New Hollander, where food is deficient, or into an 
tffeminate creature like the old inhabitants of the West Indies, where it is abundant ; 
while a civilized people with ' a care for their meat and diet,' will have thought about it, 
labore<l forit steadily, advanced science, and ransacked nature, to improve it, and ob« 
tained their reward in the search itself.' "—(Dr. Chambees). 



THE VEGETABIAN QUESTION. 407 

ganic acid, deport themselves alike, and produce exactly the same 
effects, in that most delicate and changeable of all chemical prepara- 
tions — the blood of the living body. We can hardly suppose that 
these -widely dissimilar substances would have been made so perfectly 
interchangeable under these circumstances, except to provide for the 
possibility of a mixed and variable diet. 

Y59. Indications from the Saliva. — Attention has been called to the 
saliva, as affording a possible test of the kind of food adapted to different 
animals. Human saliva is much more powerful in its action than that 
of carnivorous animals, as the dog. This evidently points to a diet 
abounding in starch as proper for man, whUe the contraiy is clearly 
indicated in reference to the dog. 

V60. Relative Economy of Vegetable and Animal Diet. — If the question 
present itself as one of economy on the largest scale, that is, under 
which diet the greatest number of human beings can be sustained on 
a given area, we must decide at once in favor of the vegetarian policy. 
All animals are organisms for the destruction of nutritive matter. 
"When an animal is slai'ghtered, it affords a mass of nutritive material ; 
but it is only a residue, —a small remaining part after life-long waste and 
destruction of food. The body of the ox represents, perhaps, thou- 
sands of bushels of grains and roots which it has consumed. If we ob- 
tained from him force, in the shape of work done, the loss was not 
total ; otherwise, a few hundi'ed weights of beef is our sole equivalent 
for the destruction of many tons of vegetable food. The amount of 
nutritive material procurable upon a given surface of the earth, is de- 
finite and limited, and the inferior animals are machines for its de- 
struction ; in consuming them, we take what happens to remain, and 
besides the previous necessary loss, the nutriment we get comes in 
the worst possible shape in point of economy (744). If grains, legu- 
minous seeds, fruits, and roots, are cultivated — nutriments adapted to 
tlie sustenance of men ; and the lower animals be dispensed with, the 
conditions are provided for the largest human population. The great 
superiority of agricultural communities in numbers and power, over 
the hunting and flesh-consuming races, is thus obvious. The case 
was pithily put by a North American Chief, who, according to the 
French traveller Crevicoue, addressed his tribe as follows : " Do you 
not see the whites living upon seeds, while we eat flesh ? That the 
flesh requires more than thirty moons to grow up, and is then often 
scarce? That each of the wonderful seeds they sow in tlie earth, 
returns them a hundred fold ? That the flesh on which we subsist has 
four legs to escape from us, while we can use but two to pursue and 



408 PHYSIOLOGICAL EFFECTS OF FOOD. 

capture it ? That the grains remain where the whites sow them, and 
grow ? That winter, which with us is the time for laborious hunting, 
to them is a period of rest? For these reasons have they so many- 
children and live longer than we do. I say, therefore, unto every one 
that will hear me, that before the cedars of our vUlage shall have died 
down with age, and the maple trees of the valley shall have ceased to 
give us sugar, the race of the little corn-sowers, will have extermi- 
nated the race of flesh-eaters, provided their huntsmen do not them- 
selves become sowers." 

761. Diversities of Diet among different Nations. — The adaptability of 
the human constitution to widely different dietetic conditions, is re- 
markable. We find among the races distributed over the globe, the 
pure vegetarians, — some subsisting upon soft fruits, others upon hard 
grains, others upon succulent herbage, and others again upon tough 
fibrous roots. On the other hand, there are the exclusive animal 
feeders, some consuming flesh, others fish, others fowl, and others 
even insects ; — some devour their food raw, others cook it ; some take 
it as soon as it has ceased to live, and others wait till it turns putres- 
cent. Thus the diet of one locality would become loathsome and fatal 
in another. It has been affirmed that this dietetic pliancy of man, 
by which he is enabled to live upon the most strangely diverse forms 
of aliment, is a wise providential design to secure the diftusion of the 
human race, and the most extended occupancy of the earth. But 
though this be admitted, it brings us no nearer to a settlement of the 
question, " What form of diet is best suited to the full and harmonious 
and highest development of man's nature ? " that is one of the large 
and serious problems to which science will address itself in the 
future. 

12, Considerations of Diet. 

762. We conclude the subject of the physiological action of foods 
with some general and practical suggestions concerning diet, partly in 
recapitulation and partly supplemental. 

763. Tlie demand for Food variable. — By recalling the purposes to 
which food is applied, we perceive how changeable must be the de- 
mand for it. It is the source of power, and therefore, with the alter- 
nations of exercise and rest, its requirement rises and falls. It is the 
source of warmth, and therefore the quantity we need must vary with 
our protection from cold. Any cooling of the body increases the 
appetite, and compels us to eat more than usual. Again, the necessity 
for food is complicated with the conditions of breathing. The waste 



CONSIDERATIONS OF DIET. 409 

of matter in the body stands in close relation to the oxygen it con- 
sumes, and this varies with capacity of the lungs, atmospheric purity 
afld density, and therefore influences the quantity of food necessary to 
restore the bodily loss. A Manchester manufacturer ventilated his 
weaving mill, when forthwith the appetites of the operatives were 
sharpened, and as their wages would just support them, they made 
formal complaint of the change, and demanded an advance of com- 
pensation. Thus the multiplex and ever-varying conditions of tem- 
perati,--e, air, a*d exercise, joined with the diverse influences of age, 
sex, constitution, temperament, and habit, conspire to determine the 
necessity for food in each special case. 

764. Diversities in Digestion and Diet.— There are also wide differ- 
ences among different persons in point of abQity to digest and assim- 
ilate food. We meet with one class — types of robust health, with 
sound, vigorous systems, accustomed to much exercise in the open air, 
and who take all kinds of food, caring only that there shall be enough. 
They never suffer the slightest inconvenience from what they eat, and 
seem indeed to be unconscious of having any stomach or visceral 
organs. All discriminations among aliments, as digestible and indi- 
gestible, with suggestions and precautions concerning diet, fall upon 
the ears of such as without signification. On the other hand, we 
behold the dismal group of dyspeptics, horribly conscious of their 
digestive arrangements, and to whom the whole world of aliment is 
tui-ned into a perennial fountain of misery. Between these two ex- 
tremes there are all degrees of digestive power and gastric suscepti- 
bility. Again we notice great diversities in plans of diet among those 
with healthy digestions. This state of things makes difficulty in 
fixing upon terms to describe different sorts of diet. Loxd diet, for ex- 
ample, is applied to a combination of food that yields less blood and 
strength than usual, while a Mgh or generous diet tends to produce a 
contrary effect. But it is obvious that a diet which would be, to all 
intents and purposes, low and spare^ to a hearty meat-eater, might be 
Mgh and generous to a strict vegetarian. To be able, therefore, to 
pronounce any particular diet abstemious ovfull, we must understand 
the preceding dietetic habits. 

765. Daily requirement of Food — These facts make it apparent, that 
all rules of diet are necessarily so general as to be of little service, 
until modified to suit the peculiar circumstances of each individual. 
Instead of blindly submitting ourselves to any scheme of dietetic 
directions, we should exercise an independent judgment, studying 
carefully our own constitutional peculiarities, analyzing our conditions, 

18 



410 PHYSIOLOGICAL EFFECTS OF FOOD. 

and freely revising all rules before reducing them to personal practice, 
We cannot fix the precise quantity of food required to be consumed. 
Where men are dealt with systematically in large numbers, as the 
inmates of hospitals, soldiers, &c., it becomes necessary to establish 
diet scales, that is, to apportion to each person his due allowance of 
food by weight and measure. The following is the diet scale of the 
U. S. Navy : Three days in the weeh ; — pork, 16 oz, ; beans or peas, 
7 oz. ; biscuit, 14 oz. ; pickles or cranberries, 1 oz. ; sugar, 2 oz. ; tea, 
\ oz. ;=40]^ oz. Two days in the weeTc ; — beef, 16 oz.; flour, 8 oz. ; 
dried fruit, 4 oz. ; biscuit, 14 oz. ; tea and sngar, 2i oz. ; pickles or 
cranberries, 1 oz. ;=45f oz. Two days in the tceek ; — beef, 16 oz. ; 
rice, 8 oz. ; butter, 2 oz. ; cheese, 2 oz. ; biscuit, 14 oz. ; tea and 
sugar, 2i oz. ; pickles or cranberries, 1 oz.=45i oz. These numbers 
are valuable as near expressions of the wants of large bodies of men, 
under given circumstances ; but they are of small service as dietetical 
guides to individuals. 

766. Regulating the Appetite. — We are left, therefore, in this matter 
entirely to individual discretion. Nature's guide is the appetite, but 
we must be cautious not to misinterpret its indications. In what 
hunger exactly consists we cannot tell. But the feeling seems to 
depend less upon the immediate state of the stomach (in respect of 
fulness or emptiness), than upon conditions of the general system. 
Hence the swallowing of food, although an immediate relief of hunger, 
does not at once extinguish the appetite. If therefore we eat slowly, 
prolonging the meal with deliberate and thorough mastication (634), 
time is given for the system to become conscious, as it were, of the 
progress of the supply, while the sense of quiescent satisfaction indi- 
cates that sufficient food has been taken, and that we should cease 
eating. If, on the other hand, we neglect these monitions, bolting the 
alimentary mass, and driving on to repletion, we incur the double 
evil of over-eating, and of taking our food in a crude, half-prepared 
state. To obtain that command of appetite which shall enable us to 
abstain before we reach satiety, is every way most desirable, both as 
a means of preserving health, and of regaining it when lost. 

767. Frequency and times of Eating. — Systematic recurrence is the 
order of nature, observed every where, alike in the timing of melo- 
dious sounds, the rhythmic beats of the heart, the measured respirations, 
the coming and going of light, the ocean's ebb and flow, seasonal revo- 
lutions and planetary periodicities. The arrangement of regular times 
for meals, harmonizes, therefore, with the universal policy of nature, 
and is, moreover, of the highest social convenience. Yet it is impos* 



CONSIDERATIONS OF DIET. 411 

Bible to subject all to the same regulations of time. Dr. Combe re- 
marks : " The grand rule in fixing the number and periods of our 
meals is, to proportion them to the real wants of the system, as modi- 
fied by age, sex, health, and manner of life, and as indicated by the 
true returns of appetite." As the blood is usually most impoverished 
after the eight or ten hours' fast of the night, breakfast should be 
early (768). The stomach is usually vacated of its nutritive contents 
in about four hours after eating, but it may be an hour or two later 
before the blood begins to call upon it for a renewed supply. Persons 
engaged in active labor, in which bodily expenditure is rapid, of course 
require to eat more often than the indolent and the sedentary ; and 
children need nourishment oftener than adults. But too long absti- 
nence, especially if the digestive power be not strong, sharpens the 
appetite, so that there arises danger of excessive eating. Some avoid 
luncheon for fear of 'spoiling the dinner,' whereas the thing they 
most need is to have it spoiled. "Where the intervals between the 
meals are so long as to produce pressing hunger, something should be 
taken between them to stay the appetite and prevent over-eating. 
Late and hearty suppers are to be reprobated. Active digestion and 
sleep mutually disturb each other, as at night the exhalation of car- 
bonic acid is slowest, and tissue changes most retarded, the overloaded 
blood is not relieved, and invades the repose of the brain, producing 
heavy, disordered dreams, and nightmare, followed by headache and 
ill-humor in the morning. StUl there is the opposite extreme, of sit- 
ting up late, and going to bed wearied, hungry, and with an 'inde- 
finable sense of sinking,' followed by restless, unrefreshing sleep. A 
little light nourishment in such cases, may prevent these unpleasant 
effects. Custom has fixed the daily number of meals at from three to 
five ; probably three is the smallest number that consists with well- 
sustained vigor of the system ; four or five may be unobjectionable, 
the amount of nourishment taken each time being less. The essential 
thing is, regularity in each case, in order that the digestive glands may 
have time to prepare their secretions (641). 

768. Best before Meals. — We should not take our meals when tired 
out, or much fatigued. The stomach participates with the other parts 
of the system in the exhaustion, and is thus unfitted for the perform- 
ance of its proper and active duties. If there has been severe exer- 
cise, either of body or mind, a short interval should be allowed for 
repose, or half an hour may be appropriated to any light occupation, 
such as dressing, before sitting down to dinner. It is questionable if 
much exercise before breakfast be generally proper. When we rise in 



412 PHYSIOLOGICAL Eli'FECTS OF FOOD. 

the morning, the system has passed the longest interval without food, 
and is at the lowest diurnal point of weakness from want of nourish- 
ment. It is well understood that the body is more susceptible to 
the morbid influence of colds, miasms, and all noxious agencies, in the 
morning before eating, than at any other time ; and those exposed to 
the open air before getting any thing to eat, in aguish regions, are in- 
finitely more liable to be affected than those who have been fortified 
by a comfortable breakfast. Cases may be quoted, undoubtedly, in 
which early exercise has produced no injurious results — perhaps even 
the contrary. Yet in most instances, especially if the constitution be 
not strong, breakfast should follow shortly after rising and dressing, 
before serious tasks are attempted. Dr. Combe justly observes, that 
in " boarding schools for the young and growing, who require plenty 
of sustenance, and are often obliged to rise early, an early breakfast is 
almost an indispensable condition of health." 

Y69. State of Blind daring Meals. — We have before seen how mental 
and passional excitement disturb appetite and digestion (685). The 
brain and stomach are profoundly sympathetic. Morbid states of the 
stomach often so disturb the brain as to throw a paU of gloom over 
the mind, or destroy its equanimity, as we often see in dyspeptics, 
while any mental tension or discord interrupts the gastric functions. 
Food has been rejected from the stomach, unaltered, several hours 
after it w^as taken, under the dread of an impending surgical opera- 
tion. During meals, therefore, every thing like intense mental exercise 
should be avoided, yet the mind ought to be lightly occupied, as in 
cheerful, exhilarating conversation upon passing topics. A flow of 
sprightly or sportive talk, that may agreeably engage the attention, 
and thus protract the meal, is not only most pleasant at table, but is 
of solid physiological service. This explains an observation of Dr. 
CnAMBEKS. " It is very common to hear bachelors complain that when 
they dine in company, their dinner gives them no trouble ; they swal- 
low all sorts of imprudent food, and feel no more of it, while a soli- 
tary meal at their club, on the plainest meat, is digested with diflS- 
culty and pain." 

770. Exercise after Meals. — "When any portion of the body is strongly 
esercised, the whole system is taxed to sustain it. Tliere is an unu- 
sual determination of blood to the excited part, with, of course, a cor- 
responding deficiency in other parts. The case of the two dogs is well 
knowm, both of which had taken a hearty meal, one being then left at 
rest and the other put upon the chase. After a short time they were 
both killed, when digestion was found far advanced in the one at rest, 



CONSIDERATIONS OF DIET. 413 

while it was not even begun in the other. The vital force required to 
promote digestion was diverted entirely to the muscular and nervous 
systems. There is some conflict of opinion as respects the propriety 
of exercise after a hearty meal, such as dinner. Dr. Beaumont says, 
" From numerous trials, I am persuaded that moderate exercise con- 
duces considerably to healthy and rapid digestion. The discovery was 
the result of accident, and contrary to preconceived opinions." Dr. 
Combe, on the other hand, observes " that active exercise immediately 
after a full meal, such as is generally taken for dinner, is prejudicial to 
its digestion, seems to be proved by daily and unequivocal experi- 
ence." We conclude that physiological indications, the widest expe- 
rience, and the analogies of nature, concur to suggest rest for a time, 
or very gentle exercise, as most advisable.* There is clearly a de- 
pression of the general functions of the body, with a tendency to slug- 
gishness and repose. Inclination to rest after eating, seems to be a uni- 
versal instinct of the animal kingdom. To tliose who are drowsy and 

* " Heading has been too mucli overlooked of late as a bodily exercise, and the benefit 
has been doubted, because of the awkward manner in which it is done. Look at a 
Greek or Roman representation of a man speaking or reading ; he is standing up, or sit- 
ting back with the chest thrown well forward and dilated, the nostrils open, and the 
shoulders flatter and more erect than when walking. The artist's model evidently has 
the lungs filled with air, and the diaphragm at rest, so that full play is given to the elas- 
tic cartilages of the ribs. The man is rolling out his words really clave, as Celsus has 
it, comfortably to himself, and agreeably to his hearers. Observe as a contrast many a 
modern reader or orator ; his constrained attitude recalls rather the architectural incon- 
gruities of Gothic art, expressing, perhaps, the earnestness and self-denial which that 
style may be held to indicate, but certainly not wholesome ease. The head is bent for- 
ward, a stiff neck-cloth compresses the windpipe, the lungs are emptied, and the words 
are squeezed out by an effort of the diaphragm and abdominal muscles, which makes the 
listener fancy he can almost hear them creak with the strain. They are used at an enor- 
mous mechanical disadvantage, and the nervous energy of the whole trunk is foolishly 
e.xhausted. Hence, reading and preaching, instead of being a relief to gastric derange- 
ment, are nowadays found actually to produce it. The clergyman's sore throat and 
dyspepsia have often been traced to their professional work, and that which might have 
been a cure has become an aggravation. There was, some years ago, a quack in the Isle 
of Wight, who used to treat clergymen very successfully, under a promise of secrecy. 
His method was simply to teach them to keep the chest inflated, by breathing in only 
through the nose, and to allow it to empty Itself by the elasticity of the cartilages as the 
patient spoke. This plan entails the habit of straightening the windpipe, sitting or 
standing upright, and throwing the shoulders back ; in fact, of assuming the attitude 
which I have described as a model for the reader, and is for that reason found practically 
beneficial. If patients causing, they possess a part of the Materia Medica very valuable 
to their digestion. They will seldom require the hints above given, for most leading 
masters have found the necessity for teaching their pui)ils a rational attitude, and the or- 
dinary time for exercising the art is the hour after the meal that most requires atteutloa 
It is striking how rarely powerful singers suffer from gastric derangement."— (Do. Guam 

SEBS.) 



414 PHYSIOLOGICAL EFFECTS OF FOOD. 

inclined to take their siesta, or after-dinner nap, we may suggest that 
it is better to sleep upright in a chair than to repose on a sofa or bed. 
In the former position the sleep is generally short, and never very pro- 
found ; but when the whole body is recumbent and the stomach full, 
the sleep is heavy, prolonged, and unrefreshing, 

771. Effects of Excessive Eating. — The consequences of uncontrolled 
indulgence of the appetite manifest themselves variously. The imme- 
diate result of over-eating is lethargy, heaviness, and tendency to 
sleep. The effect of persisting in the habit will depend upon numer- 
ous circumstances. In a healthy systeni, with good digestion and 
much active out-of-door exercise, bad results may not follow from the 
freest use of plain food. In other conditions the burden may fall upon 
the overworked digestive organs, which are irritated by the presence 
of the excess of food which they cannot appropriate. If digestion be 
strong, an excess of nutriment may be projected into the blood, over- 
loading the circulation. If food is not expended in force, the natural 
alternative is its accumulation in the system, increasing the volume of 
muscle and tissue, and swelling the deposit of fat. Degeneracy of the 
structures, mal-assimilation of nutritive material, increased proneness 
to derangement and diseased action, and various unhealthy conditions, 
may be induced by the habitual employment of too much food. It is 
either transmuted into fat and flesh, or into pain and disease. Yet it 
is very common to charge upon quantity the evils that flow from qual- 
ity in diet. Injury may spring from hearty indulgence in a rich, con- 
centrated, and various diet, which would not flow from the most lib- 
eral use of plain and simple food. ' Dine upon one dish, and in that 
consult your taste,' is an excellent motto. 

772. Effects of InsuflScient Nntrition. — The blood is the stock of ma- 
terial on hand, from whicli the supplies of the constantly wasting sys- 
tem are withdrawn, and this stock is but small. It contains dissolved 
only about one-eighth of the dry matter of the body, so that the 
strength can be sustained only a very short time without external sup- 
plies. Yet when food is withheld, life holds its ground against exten- 
sive changes. An animal does not die of starvation till it has lost two- 
fifths of its weight and more than a third of its heat. Yet, so impor- 
tant is the prompt and regular ingestion -of aliment, to keep the sys- 
tem up to the par of its activity, that even transient interruptions pro- 
duce serious disturbance. As the demand for nourishment is the prime 
necessity of our being, taking precedence of all other needs, if the 
supply be suspended, the clamors of the system for food rise at once 
ibove all other wants. Until hunger is appeased, there is disquiet ; the 



CONSIDEEATIONS OF DIET. 416 

mind traverses with less than its usual freedom, the temper is mora 
easily started, and sleep fails to invigorate as usual. There was shrewd, 
practical wisdom in the warning of Cardinal De Eetz to politicians, 
never to risk an important motion before a popular assemblage, how- 
ever proper or wise it might be, just before dinner. Of the effects of 
insufficient food Moleshott speaks as follows : " There is another in- 
stinct by which the vigor of the mind is vanquished in a more melan- 
choly way. Hunger desolates head and heart. Though the craving 
foi nutriment may be lessened to a surprising degree during mental 
exertion, there exists nothing more hostile to the cheerfulness of an 
active, thoughtful mind, than the deprivation cf liquid and solid food. 
To the starving man every pressure becomes an intolerable burden ; 
for this reason, hunger has effected more revolutions than the ambition 
of disaffected subjects. It is not, then, the dictate of cupidity or the 
claim of idleness which prompts the belief in a natural human right 
to work and food." 

773. Diet and the Capacity of Exertion. — There are evils also in the 
opposite extreme of a too restricted diet. Our strength and power of 
accomplishment is derived from the food we consume, and for high 
and sustained effort there is required a strong and generous diet. We 
cannot have something for nothing. Large exertion, physical or men- 
tal, involves active physiological change, and hearty eating, to sustain it. 
The distinguished and discriminating President of one of our largest 
collegiate institutions remarked to us, that many students required to 
be encouraged to freer living. Urged to economy by limited resources 
and misled by the partial views of those who recommend low, abste- 
mious diet as favorable to clearness of thought, they adopted a scale 
of nutriment insufficient to sustain the powers of nature in vigorous 
and protracted exercise. Existence can undoubtedly be maintained on 
a very small amount of food, but we are not concerned to know what 
that minimum of nourishment may be, as bare, inert, passive existence 
is no object. Life is of but little value except in its -purposes^ and man 
is only a man in his capability of executing them. Coenaeo, the Ve- 
netian, the Prince of ascetic heroes, lived to a great age on 12 oz. of 
food, chiefly vegetable, per day, and 14 oz. of light wine. But he 
passed " a sort of vegetable life in his palace and gondola," without 
stress or buffet, while a mere lawsuit is said to have carried off two 
of his brothers who attempted the same style of living. " Dr. Stark, 
of London, tried siniUar experiments, and got on pretty well so long 
as he had nothing to do besides weighing himself, but when he cam© 
to undergo a contested election for St. George's Hospital, it killed him 



416 PHYSIOLOGICAIi EFFECTS OF FOOD. 

outright. If tlie body is to be exposed, as it is in all modern civil 
ized life, to sudden extraordinary demands, it must be prepared fol 
them by being habituated to take in rather more than is ordinarily re- 
quired." — (Dr. Chambers.) It is charged upon the Americans that they 
are enormous feeders ; probably they eat too mucli ; but where else 
upon the globe is there such general activity, bodUy and mental? 

774. Order and Variety in Diet. — Our nature was made for variety. 
The differences of complexion, cast of countenance, expression and 
figure constantly presented to us in the human form, are infinite. The 
objects about us are endlessly and namelessly diversified, always har- 
monious, yet ever changing into new relations. We gather from this, 
that in habits and experience, man is not designed to be the slave of a 
mechanical routine, nor to fall into tame and spiritless repetition. Of 
all the systematic degradations to which he is subject, the lowest ia 
that of the soldier, who has taken formal leave of his independent 
manhood, who starts at the tap of the drum, belongs somewhere in a 
row, and lives only to be drilled and messed at the arbitrary dicta- 
tion of his superiors. In nature, we behold inflexible order working 
out eternal vai-iation ; and so in life, methodized habits should give 
rise to never-ceasing diversities. As respects diet, the materials pre- 
pared for us, although marvellously simple in composition and adapta- 
tion to our needs, are wonderfully various in form and gustatory 
properties. We have the widest and freest choice of means to ac- 
complish the same physiological end. Nature thus solicits us to 
enjoy the bounty of her resourses, which we should wisely do, not tempt- 
ing the appetite with a parade of culinary enticements, but restricting 
the dishes at each meal, and agreeably varying them at successive 
times of eating. — Prof. Moleshott, after insisting that all food partakes 
somewhat of the nature of a stimulant, has the following observations : 
— " And as the uniformity of the stimulant, even if repeated at longer 
intervals, is prejudical to its effects ; a regular arrangement of dishes, 
repeated certain days every week, is a custom not to be commended. 
If a stiff regularity only too clearly betrays a commonjilace narrowness 
of mind, such a regular repetition becomes a source of petty for- 
malism, insensibly, but all the more dangerously, repressing the free 
movements of the mind. Whoever has watched himself with atten- 
tion, will often enough have experienced how the refreshing and 
Btimulating effect of a walk is evidently lost if taken for a long time 
daily at the same hour. It is the same with uniformity in meals ; 
and while the ancient physicians used actually to assert it to be useful 
Bometimes to throw the body out of order, in accordance with thia 



CONSIDERATIONS OF DIET. 417 

doctrine, it is perfectly true that an inflexible regularity of life is by 
no means compatible with a genial freedom." 

775. Diet and CorpulencCt — The undue accumulation of fat is pro- 
moted by many causes. Privation of active exercise, too much in- 
dulgence in sleep, indolent, sedentary habits, and vrant of thought, 
favor obesity; — restless animals and industrious men are seldom 
inconveniently fat. The free use of an oily, starchy, or sugary diet, 
dispose to fattening, as also alcoholic liquors and the absorption of 
watery fluids, either by much drinking, frequent warm baths, or even 
breathing damp air. It is also frequently caused by defective diges- 
tion. There may be want of gastric power to manage the nitro- 
genous matters, the muscular fibre escaping from the stomach half 
dissolved. As a moderate diet thus proves insuflicient, it is instinc- 
tively increased, and fatty bodies being more easUy assimilated than 
the albuminous, a surplus of it is lodged in the system. The excessive 
increase of fat must be regarded as a disease, and often involves the 
constitution in much disorder. In the truly healthy organization, 
there is a perfect correspondence in capacity and power, between the 
circulation through the lungs and that of the general system (283); 
but where the fat deposit becomes largely increased, the extension of 
the minute blood-vessels to maintain the extra nutrition, destroys the 
equilibrium ; the lung circulation is inadequate to its fuU duty, the 
carbonic acid is not perfectly excreted, the blood becomes venous, the 
circulation is retarded, producing congestion, with frequent dilatations 
and degenerations of the heart. The diet best fitted for corpulency, 
is that containing the least oil, starch, or sugar. Very light meals 
should be taken at times most favorable to rapid digestion, and should 
consist of substances easy of solution and assimilation. The time of 
meals should be fixed at an early hour in the day, before exertion has 
rendered the powers of the alimentary canal languid. Breakfast 
should consist of dry toast, or still better, of sea-biscuit, and if much 
active exercise is intended, a piece of lean meat. Dinner at one, on 
meat with the fat cut off, stale bread or biscuit, and some plain boiled 
macaroni or biscuit pudding by way of a second course. — (Dr. Cham- 
bers.) Lean meat is a good diet for the aspirant after leanness ; — 
carnivorous animals are never corpulent. In connection with proper 
diet, vigorous and systematic exercise is essential. Sometimes there is 
an accumulation of fat, where the amount of aliment taken is less than 
natural. Such cases are' difficult to remedy by exercise, as the 
quantity of food taken is too small to sustain muscular strength. 

770. Diet of Infancy. — We have stated that nature prescribes the 
18* 



418 PHTSIOLOGICAIi EFFECTS OF FOOD. 

infant's diet in the composition of its mother's milk ; but nature ia 
sometimes defeated in her intention, as the mother's diet controls the 
milk-secretion both in quantity and quality. If her food be scanty, or 
low and light, the infant will be imperfectly nourished. The lactic 
secretion requires to contain its due proportion of casein, sugar, oil, 
and phosphate of lime ; and to produce these copiously, a varied 
nutritious diet of good bread, meat, milk, eggs, and potatoes, is re- 
quired. The aliment which the mother furnishes to her child is more 
richly nutritive than that which she retains for her own nourishment. 
She should avoid indigestible substances, and especially take but 
little vinegar or acid fruits, as these both diminish the amount of mUk 
and render what there is less nutritious. The nursing mother may 
with great advantage make free use of mUk itself, as it furnishes, ready 
formed, the substances she is required to impart. Should there be 
tendency to acidity, it may be corrected by mixing the milk with a 
mild alkali, such as one-fourth or one-fifth of its bulk of soda water, 
it becomes often necessary that chUdi'en should be surrendered to wet 
nurses. As the composition and consequent physiological effects of 
milk gradually change in the successive months after the child's birth, 
it is important that the ages of the children, both of tlie mother and 
wet-nurse, should be as nearly as possible the same. That nature, 
temper, and character are communicated by her milk, from the 
mother to the nursing chUd, is not an idle prejudice. Not only do 
bodily circumstances of health affect the lactic secretion, but con- 
ditions of the mind and passions also. A paroxysm of anger may 
pervert and even poison the fountain of life ; " and there is no thought 
more natural, than that on the breast of its mother the infant may 
imbibe together with its milk, her nobleness of mind." When the 
exigency occurs, therefore, the selection of wet-nurses is a matter of 
much importance. If they have been accustomed to plain, substantial 
diet, it is highly unwise to pamper them with delicacies, as is some- 
times done in affluent families, indigestion and bad bodily conditions 
being very liable to ensue. As respects the use of spirits under these 
circumstances, Dr. Cdambers, himself no advocate of abstinence, has 
the following remarks. " Nursing women are desired to drink an un- 
usual quantity of porter, wine, bitters, and what not, till they get 
bloated, thick-complexioncd, stupid, and dyspeptic. The reason of 
this is, that alcohol and other ingredients, in such a diet, arrest meta- 
morphosis, detain in the system the secretions we want to flow out, 
and fill those which do flow out with effete matter. If the con- 
stitution of tlio mother is robust enough to stand this bad usage, 



CONSIDERATIONS OF DIET. 419 

and still afford the due quantum of milk for her chUd, yet that 
must be of inferior quality to what she otherwise would have 
made, and the innocent consumer suffers." The milk of the cow 
differs so considerably from that of the mother, that it should bo 
corrected if it is to be given to the infant. This is done by adding 
a third or a fourth of water, and about l"25th its weight of refined 
sugar; it should be warmed to the temperature of the body, 98°. 
To this, solid substances may be gradually added, as wheaten bread 
or boiled farina (445), but not arrowroot, tapioca, sago, or rice, 
upon which many children are fed to death. These are not complete 
nutriments, and are incapable of promoting the growth of either bones 
or flesh (746). Even after weaning, soft mixtures of good bread 
with milk and sugar^ or with the juices of meat; also the more 
readily digestible roots and vegetables, together with soups prepared 
from the meat of young animals, may be considered the best food. 
After the teeth are cut, meat and bread in their simple form may also 
be given. Aliments difficult of digestion, fat meat, heavy bread, rich 
pastry, unripe fruit, leguminous seeds, and heating condiments are 
carefully to be avoided for children. 

777. Diet of Childhood and Youth. — Besides the maintenance of ac- 
tivity, the diet of this period must be such as to harden, strengthen, 
and expand the system. The muscles increase in fibrin and firmness, 
tissues are developed and strengthened, and the gelatinous model of the 
bones is solidified and enlarged into a strong skeleton by the gradual 
deposit of bone-earth. With these changes there is also a slowly aug- 
menting activity of bodily transformation, the excretion of carbonic 
acid by the lungs, and of urea by the kidneys, increasing in amount 
up to the twenty-fifth or thirtieth year. The demand for food is 
therefore more peremptory during the growing time of youth than 
at any portion of subsequent life. As regards the indulgence of the 
appetite at this period, perhaps there is no better guide than the indi- 
cations of natui-e. So children have plaiti food, if healthy and active, 
they will hardly eat sufficient to injure themselves. It is not right to 
subject the young to a regimen adjusted to the adult ; they require 
more nutritious food, and to satisfy the appetite oftener. Something 
to eat in mid-forenoon and mid-afternoon will often be necessary, but 
the thing should be done strictly upon system, as the habit of eating 
irregularly, at every capricious call of appetite, is wrong and injurious. 
Yet, though the diet of youth should be nutritive and strength- 
imparting, it is of the first necessity that it should be plain and unex- 
citing. Luxurious stimilatiug food, charged with condiments and 



420 PHYSIOLOGICAL EFFECTS OF FOOD. 

nerve-provocatives, gives rise to a morbid precocity of instincts, 
thoughts and actions, and helps to exphiin the unhealthy prematurity, 
the slender figures and pale faces of boys and girls brought up in 
towns. 

778, Diet of Middle Life. — When maturity has been reached, there 
comes a period, varying in duration, but extending perhaps from the 
ages of 25 to 45, in which the bodily exchanges are in equilibrium — 
the expenses and receipts of nutrition are balanced, and the individual 
neither gains nor loses weight. No portion of the food is now to be 
appropriated as heretofore in growth ; it may all be devoted to exer- 
tion. It is the time of maximum power, the effective working period 
of life. The diet should be varied and strong, but of course ought to 
be modified in accordance with the activity, constitution and various 
cii'cumstances. For hard, exhausting labor, brown or lean meat, the 
leguminous seeds, bread, and an admixture of vegetables may be em- 
ployed. It can hardly be necessary to add in the light of the princi- 
ples of nutrition which have been established, that fat pork is gen- 
erally much over-estimated by laborers ; it is the blood-producing 
beans and bread with which it is always associated that chiefly im- 
parts the strength. It has been sufficiently pointed out that persons 
in light sedentary occupations, brain-workers and idlers, should avoid 
those more indigestible substances, and while reining in the appetite, or 
at all events, not spurring it, should live upon a diet of the most easily 
digestible substances. 

779. Diet of Advanced Life. — As age comes on, the nutritive condi- 
tions of youthhood are reversed, the body can no longer digest and 
appropriate sufiicient to meet its destructive losses, and there is a 
decrease of strength and weight. The tissues shrink, as we see in the 
shrivelled hands and wrinkled brow, the hair is changed in compo- 
sition, the bones become more earthy and brittle, the cartilages ossify, 
there is a general diminution of fat, and a loss of fluids in aU parts 
except the brain, which becomes more watery. The stomach partici- 
pates in the general decline, its diminished and weakened juices be- 
coming less capable of dissolving the necessary food ; the circulation 
is retarded, and the general vitality lowered. As the solvent powers 
of the stomach begin to be enfeebled, and the appetite becomes languid, 
elderly people should be admonished to exercise care iu selecting food, 
and not waste the power they have on refractory indigestible aliments. 
Young and tender meats, strong broths, milk, liglit, well-baked bread, 
and tender succulent vegetables, tax the digestive organs least. Nof 
Bhould they commit the error of supposmg that the waning powera 



CONSIDERATIONS OF DIET. 421 

of advancing life can be sustained by inci"easing the quantity of food 
eaten. Dr. Chetne remarked more than a liundred years ago, 
" Every man after fifty ought to begin to lessen the quantity of his 
aliment ; and if he would avoid great and dangerous distempers, and 
preserve his senses and faculties clear to the last, he should go on 
every seven years abating gradually." "When hints like these are 
neglected, and persons persist in a high and hearty diet, keeping up a 
plethoric state of the system, serious and fatal consequences often 
ensue. The blood-vessels of the brain are not only weaker than those 
of any other part of the body, but they derive no support as other 
vessels do from the elastic pressure of surrounding muscles. In the 
imperfect nutrition and growing debility of advancing age, these ves- 
sels participate, so that with over-fulness there arises liability of their 
giving way, as in brain congestion or apoplexy. 



PART FIFTH. 

CLEANSING. 

- « — 

I.— PRINCIPAL CLEANSING AGENTS. 

780. Chemical Principles involved, — Dirt has been laconically defined 
as ' matter in the wrong place ' ; its removal constitutes ' cleansing.' 
The action of cleansing agents, and the management of cleansing pro- 
cesses, depend upon the properties of solvents and the operations of 
solution and decomposition, and therefore involve questions of chemis- 
try. We have had frequent occasion, in the preceding pages, for the 
aid of this science in elucidating the phenomena of the household, and 
we shall none the less need a knowledge of it to understand the pres- 
ent subject. The considerable space given to aliments makes it ueces- 
saiy to restrict our treatment of this topic within narrow limits. 

781. Water as a Cleansing Agent. — This is the most important and 
universal of the agents of purification employed by art. It is so essen- 
tial to life, that where man dwells it is always found, and is supplied 
by the hand of nature with a copiousness equal to its necessity and 
value. Water cleanses by its mechanical action in carrying away dirt 
and impurities, and also by its power of dissolving them. WhUe it 
possesses the property of dissolving a great number of substances, it 
is at the same time so mild and neutral as not to injure the objects to 
which it may be applied. 

782. Cleansing of Water. — But before water can be used for cleansing 
purposes, it may itseJf require to be cleansed. We have already stated 
that it is liable to many forms of impurity. It is often desirable to 
remove these contaminations by artificial means, and thus make the 
liquid purer, which may be done in various ways. The foreign sub- 
stances of water are of two kinds ; first, finely divided earthy matters, 
as sand, clay, lime, &c., and particles of vegetable and animal sub- 
stances, as of decayed leaves, decomposing wood, insects, &c., diffused 



PILTBATION OF WATER. 423 

through the liquid and mechanically suspended in it, causing it to 
appear more or less turbid or cloudy ; and second^ various dissolved 
substances which contaminate the water, while it is yet clear to the 
eye and apparently pure. 

783. Purification by Subsidence. — The first sort, or mechanical impu- 
rities, if the water is kept perfectly still, will mostly subside, forming 
sediment ; the heavier particles falling first, and the finer afterward. 
It is wisely arranged that there are but few substances of exactly 
the same specific gravity as water ; if there were, this fluid would 
scarcely ever be clear. But there are many particles which find their 
way into water that are so near its precise weight, that they remain 
long suspended, and hence we must resort to other means for their 
removal. 

784. Purification by Filtering. — "Water strained or leached through 
soils and sand-beds comes out free from mechanical contaminations ; 
hence if made to percolate through artificial sand-beds, it may be de- 
livered clear. A cistern may be divided into two compartments by a 
partition which does not reach quite to the bottom. In one of the 
divisions is put layers of sand, of different degrees of coarseness, the 
finest being at the bottom. The water is poured into these apart- 
ments, trickles through the layers, its impurities are detained, and it 
comes out into the other division clear. After a time the sand gets 
clogged with sediment, and needs to be renewed. 

785. Upward flow of Water through Filters. — Through nature's filter- 
beds water ascends^ rising to the surface in 
springs, «fec. This is better, as their weight 
tends to oppose the ascent of the impuri- 
ties which are more likely to be left behind. 
The arrangement may be made available 
in many ways ; the principle is illustrated 
in Fig. 124. In the cistern or vessel the 1 =l^f ^'"'^A ■J_?T> 
partition a does not reach quite to the hot- ^^^^S«s^^.^^^ 
torn. The middle division has a perforated bottom of metal or wood, 
above which is placed a layer of sand, and upon that a layer of char- 
coal. In the partition 5, and above the filter, is an aperture through 
which the filtered water passes, and is drawn off by the foucet. Wliero 
rain water is to be preserved for household use (380), an underground 
cement tank sliould be constructed to store it, and a filter similar to the 
one described placed above, through which the water from the roof 
Bhould flow to the reservoir. Filters may be cleansed by reversing the 
iu-ection of the water through them. The principle of filtration is 




424 PELNCIPAL CLEAWSING AGENTS. 

80 simple that any vessel can be made to answer for it, tall ones being 
preferable to shallow. A box, cask, jar, or flower-pot may, with the 
least ingenuity, be made to serve the purpose. Besides sand, porous 
stone, pounded glass, woollen cloths doubled thickly, sponge, &c,, 
are used for filtering. But by far the most valuable agent for the pur- 
pose is charcoal. Its purifying action goes much further than merely 
straining out mechanical impui'ities ; it acts powerfully to absorb and 
destroy offensive gases (811). The foulest ditch water made to pass 
through a layer of charcoal, comes out sweet, clear, and bright. Ani- 
mal charcoal, derived from buritt bones, is more powerful than wood 
charcoal, owing, perhaps, to the fact that its mineral matter acts as a 
divisor, separating the particles and exposing a larger surface. 

786. Impurities in Solution. — But the dissolved impurities of water 
cannot be removed by filtering ; it is more difficult to separate these. 
By vaporizing, water leaves its impurities behind. Steam conducted 
away and condensed in a separate vessel, produces distilled water, 
which is its purest form. A tube of copper, glass, or gutta-percha, 
connected with the spout of a tea-kettle, and surrounded by cloths 
kept saturated with cold water, affords a rude but couveuient means 
of preparing the purest water. The removal of dissolved impurities 
by other means depends upon the special nature of the dissolved sub- 
stance. Thus, carbonate of lime or limestone, is dissolved in but a 
small degree by pure water, but water containing carbonic acid dis- 
solves it freely, in proportion to the amount of the contained gas. It 
has been found that one gallon (70,000 grains) of pure water will not 
dissolve more than two grains of carbonate of lime. But by the ad- 
dition of carbonic acid, it acquires the power of dissolving 10, 20, or 
60 grains, as the case may be. The number of grains contained in 
a gallon has been adopted to express the ''degree of hardness ; ' thus, 
10 grains would correspond to 10 degrees of hardness, 20 grains to 20 
degrees, and so on. By boiling, the carbonic acid is driven off, the 
carbonate of lime precipitates or falls, and the water is softened. This 
is the source of the thick fur which gradually accumulates on the in- 
ner surface of tea-kettles in limy districts. But all the carbonate is 
not at once precipitated when the water is raised to boiling ; it may, 
indeed, take two or three hours of brisk boiling to separate aU the 
lime that is capable of being thus removed. It has been found that 
water of 14 degrees of hardness lost two degrees when merely made 
to boil ; boiling for five minutes reduced the hardness to 6 degrees, and 
for a quarter of an hour to a little more than four degrees. There is, 
therefore, reason in the antiquated habit of letting the tea-kettle boil 



ALBLALESTE SUBSTANCES. 425 

for some time before the tea is made ; it softens the water (533). "We 
may relieve water of one impurity by adding another, and the ex- 
change is often desirable, as when we wish to convert hard water into 
soft. If water be hard from carbonate of lime, the addition of a little 
caustic lime (wet to the consistence of cream) will absorb the excess 
of carbonic acid, and the insoluble carbonate will separate ; the dan- 
ger is that there wiU be an excess of caustic lime, so that the softened 
water will be corrosive. If water be hard from sulphate of lime, it is 
softened by the addition of potash, or soda, which decomposes the lime 
compound combining with its sulphuric acid. The new compound 
is not decomposed by soap (794). 

787. Alkaline Sabstances for Cleansing. — But there are many sub- 
stances upon which water will not act ; other agents must therefore 
be called in to aid it. The alkalies, potash, soda, and ammonia, are 
most powerful chemical bodies, decomposing a great many different 
compounds, especially every thing of a vegetable and animal nature. 
But they are far too strong for ordinary use, as they not only remove 
dirt and impurities, but corrode and injure the fabrics or objects which 
it is desired to cleanse. The alkalies, when pure, from their hot, cor- 
rosive, disorganizing nature, are called caustic. But we do not meet 
with pure alkalies ; the ever-present carbonic acid of the air combines 
with them, forming carbonates. But as the carbonic is a very weak 
acid, it only neutralizes them in a partial degree, their carbonates be- 
ing very powerfully alkaline. "When the alkalies are commonly spoken 
of, it is their carbonates that are meant. The alkaline carbonates dis- 
solve readily in water, forming ?ey. Soda is of a weaker nature than 
potash, less liable to injure, and therefore better fitted for detergent 
uses. Ammonia is an alkaline gas, called the volatile alkali ; it is 
adapted for use in all cases where a gaseous alkaline agent is required. 
Its common form, however, is aqua-ammonia^ or solution in water, 
which absorbs a large amount of it. 

788. Tlie Alkalies Modified— Soap. — ^Alkali is the principal agent of 
cleansing in most domestic operations, the chief question being how 
to restrain and regulate its power. Soap is an artificial compound of 
alkali with the acids of oil or fat (195), by which the alkaline energy 
is to any required degree masked or subdued. The theory cf soap- 
making {sapanijication) is, that the alkalies decompose the oils, setting 
free their basic part or glycerin, which is lost, and combining with 
other acids, forms alkaline salts ; soap is therefore really a salt. 

789. How Soap is made.— The alkalies require to be in a caustic 
state, which is produced by dissolving them and passing the solution 



426 PRmciPAL CLEANsma agents. 

(ley) tbrougli newly slaked lime, which takes away their carbonia 
acid. Soap may be made by the alkalies iu theix* condition of carbon- 
ate, but just so far as the alkali is neutralized by the carbonic acid, it 
becomes useless for soap-making. In the caustic ley the fots aro 
boiled, their glycerin is set free, and the fatty acids combining with 
the alkali, form soap, which exists as a solution in the water. To ob- 
tain it in a solid form, the solution is boiled down to a certain degree 
of concentration, when the soap ceases to be soluble, and rises to the 
surface in a soft, half-melted state. This being drawn otf into moulds, 
cools, and forms hard soap. If soda ley is used, the soap may be sep- 
arated from the water, in which it is dissolved, by adding common 
salt, which forms a brine and at once coagulates the soap. If potash 
ley is used, the addition of salt decomposes the potash soap, and forma 
a soap of soda. — {Class-looh of Chemistry/.) 

790. Hard and Soft Soap. — Soaps are thus of two kinds, hard and 
soft, this condition being influenced both by the fat and alkali em- 
ployed. The firmer and harder the fat, the solider will be the result- 
ing soap. With the same alkali, therefore, tallow will make a harder 
soap than palm or olive oil, and stearic acid than oleic acid. But the 
consistence of soaps depends far more upon the alkali employed. Pot- 
ash is very deliquescent, that is, has a strong attraction for water, so 
that when exposed it will absorb it from the air and run down into a 
fluid or semi-fluid state. The potash retains this water in the condi- 
tion of soap, so that potash soaps are always liquid and soft. The 
hard soaps, therefore, all contain soda, those with tallow or stearic acid 
being the hardest. Potash soaps will not dry, but retain their soft, 
jelly-like condition, while some kinds of soda soap become so hard by 
drying that at last they can be pulverized. 

791. Water in Soap. — Soap has a strong attraction for water, and 
may retain from 50 to 60 per cent, of it, and still remain in the solid 
state. Even when dry and hard, it holds from 25 to 30 per cent, of 
water. The customer is therefore interested to purchase old, dry 
soap, while the vender of course finds his advantage in selling it with 
as large an amount of water as possible ; and hence often keeps it in 
damp cellars, in an atmosphere saturated with moisture, to prevent it 
from drying. The quantity of water contained in a sample is easily 
determined, by cutting the soap into thin slices, weighing, and drying 
at a temperature not exceeding 212°. It is impossible, however, in 
this way, to separate all its water. Its proportion of water influences 
the solubility of soap. Some dissolve so freely in washing as to waste 
rapidly when used, while others possess the opposite quality — as, for 



COMPOSITION AND VARIETIES OF SOAP. 427 

example, "the small cubic mass of white, waxy, stubborn substance, 
generally met with on the washing stands of bedrooms in hotels, and 
which, for an indefinite period, passes on from traveller to traveller, 
each in turn unsuccessfully attempting, by various manoeuvres, and 
diverse cunning immersions in water, to coax it into a lather." Hence, 
although, as a general rule, old, partially dried soap is preferable, yet 
it may be so dry and insoluble, as to involve too great labor in rub- 
bing it into a lather; and to injure articles by excessive friction, with 
large chance of failure in the cleansing operation. Business compe- 
tition, and the demand for low-priced articles compel manufacturers 
to furnish soaps with a large excess of water ; but these cheap soaps 
may not be the most economical. 

792. Varieties of Soap. — Common yellow hard soap, consists of soda 
with oil or fat and resin. Resin is a feeble acid, capable of combining 
with alkali, but neutralizing it less completely than oil, so that the 
compound or soap formed, is too powerfully alkaline. But when 
resin is worked with an equal or larger proportion of oil, it makes an 
excellent soap for many purposes. Genuine castile soap consists of 
olive oil, saponified with soda, and colored ; that which is commonly 
sold under this name, however, is an imitation, made with common 
fatty materials. Windsor soap consists of tallow, a small proportion 
of olive oil and soda. Ordinary wliite soap or c^ird soap consists of 
tallow and soda. Cocoa-nut oil forms a soap that gives a strong 
lather. Toilet soaps are made with lard, almond oil, palm oil, olive 
oil, or suet, combined either with soda or potash, accordingly as they 
are desired to be hard or soft, and with as little excess of alkali as 
possible. They are colored and perfumed to taste. Fancy soaps are 
essentially common soaps, mixed with different aromatic oils and 
coloring substances, and diversified in form so as to suit the fashion 
of the day. Soaps are mottled, streaked or stained, by metallic 
oxides, chiefly oxides of iron ; which can only be worked through the 
body of the soap, to give it the desired marbled appearance, wlien it is 
of a certain consistence ; such soaps, therefore, cannot be charged 
with an excess of water. Transparent soap, is white soap that lias 
been dissolved in alcohol ; in addition to the detergent properties of 
the soap itself, it joins the alcohol, which is sometimes useful for 
cleansing purposes, and always harmless. But it wastes rapidly, and 
i;;s advantages hardly compensate for its extra cost. Besides water 
and soap, the universal and most important agent, otlier substances 
are also employed for special ^u^poses, which we shall notice in con- 
nection with their applications and uses. 



428 CLEA2fSING OF TEXTILE ABTICLB3. 



II.— CLEANSING OF TEXTILE ARTICLES. 

793. Composition of the Dirt. — The general principle of cleansing 
away all dirt, spots, and stains, consists in applying to them a sub- 
stance wliich shall have a stronger attraction for the matter composing 
them, than this has for the cloth or surface to which it adheres. The 
dirt is to he dissolved, and hence for each special form of impurity we 
require, if possible, to find. special solvents. It is a matter of chemical 
affinities. In cleansing textile articles, for example, we desire to 
remove the dirt without injuring the fibre of the cloth ; and if it be 
possible, without disturbing the color. Alkalies are able to dissolve 
almost every thing that presents itself in the form of dirt, but they 
are too powerful, discharging colors and corroding the tissue. In 
soap, their activity is so restrained that they become generally avail- 
able for cleansing purposes. The leading cementing constituent of 
dirt upon our garments, is some form of oily substance communicated 
Dy perspiration or contact of the skin, which is constantly covered 
by an oleaginous film. The oily, greasy basis of dirt, may be de- 
rived from many sources. But water has no affinity for oily matters 
in any form, and cannot dissolve them or alone remove them from 
any surface to which they may adhere. This is readily efiected by 
soap, which being always alkaline, takes direct eifect upon the grease, 
partially saponifies it and forms with it a compound which dissolves 
in water. The oily nature of the soap also increases the pliancy of 
the articles with which it is washed. 

794. Reactions of Soap and Water. — Water is the common liquid 
vehicle of cleansing, and soap the agent resorted to, to render dirt 
soluble in water. The soap is either applied directly to the article it 
is desired to cleanse, or it may be first dissolved in water. As soap 
and water thus act jointly, it is proper to inquire as to their behavior 
toward each other. If the water be pure or soft, soap dissolves in it 
entirely ; if it be hard, that is, if it contains sulphate of lime or mag- 
nesia, the soap, wheo added, instead of dissolving, curdles or is de- 
composed, and a new soap is formed, which contains lime instead of 
potash or soda. This new lime soap will not dissolve, and may be 
seen upon the surface of the water as a kind of izreasy scum. It 
adheres to whatever is washed in it, and gives that unpleasant sensa- 
tion called harshness when we wash our hands. Hence, with hard 
water, an excessive quantity of soap is required, while the operation 
is much less agreeable and satisfactory than with soft water. To test 
its quality of harshness, dissolve a little soap in alcohol and put a few 



STRUCTURE OF THEIR ULTIMATE FIBRES. 



429 



Fig. 125. 




drops in the water it is wished to examine. If it remains clear, the 
water is perfectly soft ; if it becomes cloudy or opaque, the water is 
ranked as hard, and according to the degree or density of the cloudi- 
ness, is the hardness of the water. 

795. Cotton, Linen, and Woollen articles. — All textile articles are, 
however, not to be treated alike in cleansing. There is a radical dif- 
ference in the structure of the fibre between woollen fabrics on the 
one hand, and cotton and linen on the other, which makes it necessary 
that they should be differently man- 
aged. Fig. 125 represents the straight 
smooth form of linen and cotton fila- 
ments, while Fig. 126 exhibits the 
toothed and jagged structure of 
woollen fibres. It is evident that 
these, by compression and friction, 
will mat and lock together, while 
the cotton and linen fibres, having 
no such asperities of surface, are in- 
capable of any thing like close me- 
chanical adherence. Hence, the pe- 
ci;liar capabilities of woollen fabrics, 
of felting^ fulling, and shrinking, 
caused by the binding together of the ultimate filaments. We see 
therefore, the impolicy of excessive rubbing in washing woollen fabrics, 
and of changing them from hot to cold water, as the contraction that 
it causes is essentially a fulling pro- 
cess. The best experience seems to 
indicate, that woollen cloths should 
never be put into cold water, but al- 
ways into warm; and if changed 
from water to water, they should go 
from hot to hotter. In the most 
skilful modes of cleansing, and pre- 
paring delaines for printing, the plan 
is, to place them first in water at 
100° or 120°, and then treat them 8 
or 10 times with water 10° hotter in 
each case. Some soak articles in warm water, to which a little wheat- 
bran has been added over night. The dirt is loosened, perhaps by a 
kind of fermentation. Soaking in weak soda-water is useful, but too 
free a use of alkalies shrinks the fibres of cloth and impairs the 



Cotton fibres. 



Linen fibres. 



Fig. 126. 




Woollen fibres. 



430 CLEANSING OF TEXTILE ARTICLES. 

Btrength of the tissue. Resin-soap should not be emplo} ed to wash 
woollen, as the resin has the effect of hardening the fibres. Delicate 
textures, and especially wliite linen, should never be boiled in hard 
water. The carbonate of lime precipitated by boiling (78G) is not 
only itself deposited upon the fabric, but carries down with it whatever 
coloring matter happens to exist in the water, and fixes it upon the 
fabric, imparting to it a disagreeable, unremovable dirty hue. 

796. Removal of Stains, Spots, &c. — To do this without injury to the 
color or the fabric, is sometimes easy, frequently most difficult, and 
often impossible. Much may depend upon skilful and persevering ma- 
nipulation ; and although various agents, which we are now to men- 
tion, are oftentimes valuable, yet good soap, after all, is the chief re- 
liance. Grease-spots may generally be removed by the patient appli- 
cation of soap and soft water, but other means are also employed. 
Alumina^ or the pure principle of clay, has a strong attraction for 
fatty substances, and is much used in the form of fullers' earth, a fine- 
grained clay, which is prepared by baking and elutriation. It is used 
by diff"using a little througli water, so as to form a thin paste, spread- 
ing upon the stain, and leaving to dry ; the spot then only remains to 
be brushed. French ehallc, a very resinous mineral, is also highly ab- 
sorbent of grease. Ox-gall is an excellent and delicate cleansing agent. 
It is a liquid soda soap. It removes grease, and is said to fix and 
brighten colors, though it has a greenish tinge, which is bad for the 
purity of white articles. The application of a red-hot iron closely 
above a grease-spot often volatilizes the oily matter out of it. Brown- 
paper pressed upon a stain with a warm iron, will often imbibe the 
grease. Stains by wax, resin, turpentine, pitch, and substances of a 
resinous nature, may be removed by pure alcoliol. The fats, resins, 
and unctuous oils, are dissolved by essential oils, as oil of turpentine. 
Common spirits of turpentine, however, requires to be purified by re- 
distillation, or it will leave a resinous stain upon the spot where it is 
used. "When pitch, varnish, or oil-paint stains have become dry, they 
should be softened with a little butter or lard, before using turpentine 
and soap. Burning-fluid combines the solvent powers of both alco- 
hol and turpentine. Fruit-stains, wine-stains, and those made by col- 
ored vegetable juices, are often nearly indelible, and require various 
treatment. Thorough rubbing with soap and soft water ; repeated 
dipping in sour butter-milk, and drying in the sun; rubbing on a 
thick mixture of starch and cold water, and exposing long to sun and 
air, are among the expedients resorted to. Sulphurous acid is often 
employed to bleach out colors. It may be generated at the moment 



REMOVAL OF STAINS. 431 

of using, by burning a small piece of sulphur in the air, under the 
wide end of a small paper funnel, whose upper orifice is applied near 
the cloth. Coffee and chocolate stains require careful soaping and 
washing with water at 120°, followed by sulphuration. If discolora- 
tion has been produced by acids, water of ammonia should be applied ; 
if spots have been made by alkaline substances, moderately strong 
vinegar may be applied ; if upon a delicate article, the vinegar should 
be decolorized by filtering through powdered charcoal. For iron 
mould, or ink stains, lemon-juice or salt of sorrel (oxalate of potash) 
may be used. If the stains are of long standing, it may be necessary to 
use oxalic acid, which is much more powerful. It may be applied in 
powder upon the spot, previously moistened with water, well rubbed 
on, and then washed off with pure water. It should be effectually 
washed ou^, for it is highly corrosive to textile fibres. The staining 
principle of common indelible iiiTc is nitrate of silver. It may be re- 
moved by first soaking in a solution of common salt, which produces 
chloride of silver, and afterwards washing with ammonia, which dis- 
solves the chloride. 

III.— CLEANSING OF THE PEKSON. 

Y97. Structure and Offices of the Skin. — A glance at the curious and 
beautiful structure of the skin, and its important offices, will assist ua 
to understand the causes 
and nature of its defile- 
ments. The outer layer 
of the skin (cuticle) is ^ \ t^ 

formed of albuminous ^ i.--.^^.-- 

cells, which, losing their ^. ""^-^ 

liquid contents by evapo- ^^ ""^^ 

ration at the surface, are ~~"-^;; A ■ - ^^^ 

flattened into exceeding- "---* , \ , ■ - V^ 

ly minute thin scales, of 
a horny, resisting quality, '^--^., . 
which serves as a pro- >^i:-'',' '\ ) 
lection to the sensitive ^3f \- 
or true skin underneath. V- _ v - • 

The surface of the cuticle "~ — --^^'^ ' 

is constantly loosening Surface of the cuticle erreatly magnified, sliowing 
*' °' the pores and hairs. 

and wearing off in fine, 

powdery scales, which are replaced by new growths from below. 

Figs. 127, 128, exhibit the structure of the skin. It is an organ of 




432 



CLEANSING OF TUE PEKSON. 



Fio. 12S. 



drainage, with a double function ; co-operating, with the kidneys, on 
the one hand, to relieve the system of water, and with the lungs on 
the other, to extrude its gases. The perspiratory tubes, which open 

through the cuticle upon the 
surface, forming pores, are spi- 
ral-shaped, as shown in the fig- 
ure, and terminate in glands be- 
low. Prof. Wilson says, "I 
counted the perspiratory pores 
on the palm of the hand, and 
found 3528 in a square inch. 
Each of these pores being the 
aperture of a little tube, about a 
quarter of an inch long, it fol- 
lows, that in a square inch of 
skin on the palm of the hand, 
there exists a length of tube 
equal to 882 inches. I think 
that 2800 might be taken as a 
fair average of the number of 
pores on the square inch, and 

Vertical section of the skin, greatly magnified : 700 the number of inches in 
a the cuticle, outer, or scarf skin: &rf the true , 1.1^-1 i i /• j? 

skin; c oil-tube and gland; 6 sweat glands and length tor the Whole SUrtace Ot 
their ducts, the outlets at the surface being ^ijg ^j^jy ^^ ^^^ number of 
the pores ; / hairs ; g cellular substances. •' 

square inches of surface, in a man 
of ordinary height and bulk, is 2500 ; the whole number of pores, there- 
fore, is 7,000,000, and the amount of perspiratory tube 48,600 yards, or 
nearly 28 miles." Twenty or thirty ounces of perspiration escape 
through these channels daily, and upon evaporating into the air, leave 
a residue upon the surface, of animal and saline matter, consisting of 
acids, alkalies, calcareous earth, &c. 

798. Impurities of the Skin. — "We have noticed the enormous ex- 
haling and absorbing surface of the lungs (283), and the consequent 
danger to which we are exposed by the inhalation of foreign, poison- 
ous substances, from the air. Evidently, if the skin were in the same 
condition, if its millions of little mouths were constantly and freely 
open to the air, the danger from absorption of infectious matter would 
be greatly heightened. But this consequence is wisely guarded against 
by a set of glands, whose special office it is to secrete oily matter to 
bedew the surface of the body. We notice that where this oily coat- 
ing is in excess, it often gives an unseemly polish to the features ; 




MANAGEMENT OF TUE SKIN. 



433 



while if it be deficient or absent, tbe skin is dry, barsb, and rough. 
Now this oleaginous pellicle, while offering no hindrance to exhala- 
tion^ or the outward escape of waste matter, protects the system 
against too free absorption from without. It is this oily distilraent, 
perpetually covering the cutaneous surface, that seizes upon all forms 
of dirt and impurity, cementing them into an adherent layer of dirt, 
comprising also the dregs of perspiratory evaporation, and the scales 
of scarf-skin just noticed. This crust of dirt may at length accumulate 
and consolidate, until it obstructs the pores, arrests free drainage, and 
thus seriously interferes with the functions of the skin, and the health 
of the body. As a consequence of the neglected state of this organ, the 
sedentary and irregular habits of refined society, the unctuous sys- 
tem of the skin becomes sluggish, and its actions torpid Fig. 129. 
and irregular, and instead of the constant flow through 
the oil-tubes, their contents become dry, dense, impacted, 
and do not freely escape. They accumulate in the ob- 
structed passages and form pimples. When those are ^^l^^ 
squeezed between the finger nails, there issues a little 
cylindrical mass of white unctiious matter, which, when 
examined with the microscope, reveals a little animalcula, 
represented by Fig. 129. It is called by Dr. "Wilson, 
who has studied its history and habitudes for six months 
at a time, stcatozoon folliculorum ; that is, the 'animal of 
the oily product of the skin.' These little personages are 
caterpillar-like, with head, feelers, four pair of legs, and 
a long tail. They are about the l-45th of an inch in 
length, and always occupy the same position iu the oil- 
tube, the head being directed inwards. The little mass 
shot out from the pimple may contain from two to twenty 
of them. 

Y99. Cleansing of the Skin— Ablution. — As oil is the basis of the coat- 
ing of dirt which daily concretes upon the skin, it is obvious that 
water alone is incapable of removing it. Soap is the proper skin- 
detergent. It partially saponifies the oil, rendering it miscible and 
soluble in water. The alkaline element of soap also softens and dis- 
solves a part of the cuticle which, when rubbed oflp, carries with it the 
dirt. Thus any washing with soap removes the face of the old scarf- 
skin and leaves a new one. If the hands are too long exposed to the 
action of an alkaline soap, they become tender, that is, the cuticle 
dissolves away, and gets so thin as not to protect the inner or sensitive 
skin. Wash powders are inferior to soap, and injure the whiteness 
19 



434 CLEANSING OF THE PERSON. 

and purity of the skin. If soap produce irritation, it is because the 
skin is in some way morbid. It should tlicn be used in small quantity 
at first, increasing it gradually. 

800. Philosophy of wasliing the Face. — Dr. "Wilson thus pleasantly 
discourses on the art and mystery of cleansing the face. " And now, 
dear reader, having determined to wash your face, how will you set 
about it ? there are many wrong ways of effecting so simple a pur- 
pose ; there is but one right way. I will tell it to you. Fill your 
basin about two-thirds full with fresh water ; dip your face in the 
ft-ater, and then your hands. Soap the hands well, and pass the 
soaped hands with gentle friction over the whole face. Havmg per- 
formed this part of the operation thoroughly, dip -the face in the water 
a second time, and rinse it completely : you may add very much to 
the luxury of the latter part of the process by having a second basin 
ready with fresh water to perform a final rinsing. And now you will 
say, ' What are the wrong ways of Avashing the face ? ' "Why, the 
wrong ways are — using the towel, the sponge or flannel as a ineans 
of conveying and applying the soap to the face, and omitting the 
rinsing at the conclusion. If you reflect, you will see at once that the 
hands are the softest and the most perfect means of carrying the soap, 
and employing that amount of friction to the surface with the soap 
which is necessary to remove the old and dirty scart^ and bring out 
the new and clean one from below. Moreover, the hand is a sentient 
rubber, or rubber endowed with mind ; it knows when and where to 
rub hard, where softly, where to bend here or there into the Httle 
hollows and crevices where dust is apt to congregate ; or where to 
find little ugly clusters of black-nosed grubs, the which are rubbed 
out and off, and dissolved by soap and friction. In a word, the hand 
enables you to combine efiicient friction of the skin with complete 
ablution ; whereas in every other way ablution must be imperfect. 
Then, as regards drying the face, a moderately soft and thick towel 
should be used ; a very rough towel is not desirable, nor one of thin 
texture. This is a point that may be safely left to your own taste and 
feelings. The question of friction during the drying is of more con- 
sequence, and this is a reason why the towel should be moderately 
soft, that you may employ friction and regulate the amount. "With a 
very rough towel it is impossible to use friction, for its tenderest pres- 
surg may be enough to excoriate the skin ; and a very soft towel ia 
equally ope-n lo objection from its inadequacy to fulfil the obligation 
of friction during the process of drying. In washing tlie face you 



SUBSTANCES ACTING UPON THE TEETH. -loS 

hare three objects to fulfil — to remove the dirt, to give freshness, 
and to impart tone and vigor to the skin." 

801. Cleansing the Teeth. — The eftect of talking, singing and breath- 
ing through the mouth, is to evaporate the water of the saliva, leaving 
its solid constituents, animal matter and salts, as a residue which accu- 
mulates upon the teeth as tartar. This, together with the fragments 
of the food which get lodged in the cavities between the teeth, is a 
constant cause of impurity in the mouth, which should, therefore, bo 
often cleansed. Dentifrices are preparations of liquid, paste and pow- 
der for cleansing the teeth. Some act chemically to dissolve the tar- 
tarous incrustation, as dilute muriatic acid, which also removes dis- 
colorations and whitens the teeth. But it also corrodes their enamel, 
and rapidly destroys them. Its habitual or frequent use is, therefore, 
most pernicious. It may be rarely and cautiously employed to efface 
dark spots or black specks upon the teeth, but it should be quickly 
neutralised with chalk, and washed away with water. Tooth pow- 
ders, which act mechanically, are better. They require to have a cer- 
tain degree of hardness or grittiness to enable them to remove the 
foreign substances adherent to the teeth ; but if too hard, they injure 
the enamel. The powder of ground pumice stone is employed, but it 
is too sharp for any thing more than exceptional use — say once in two 
or three months. Chalk is soft and excellent ; not common chalk 
pulverized, for that contains flinty particles, but prepared chalk of the 
di'uggist. Charcoal and powdered cuttle fishbone are good tooth de- 
tergents. Yet all insoluble powders are liable to the objection, that 
they accumulate in the space formed by the fold of the gum and the 
neck of the tooth, presenting a colored circle. The powder is there- 
fore often colored red with carmine or dole armeniac, Myrrh^ cin- 
namon, &c., are added as perfume. BJiatany, cinchona, and catechu^ 
are added to exert an astringent and hardening effect npon the 
gums. If substances are required which shall dissolve in using, 
tulphate of potash^ pJiospJiate of soda, cream of tartar, and com- 
mon salt may be used. Disinfecting and deodorizing tooth-powders 
and washes which destroy the unpleasant odor of the breath, and 
tend to whiten stained teeth, owe their efficiency to chloride of lime 
(807). Such a preparation may be made by mixing one part chloride 
of lime with twenty or thirty of chalk. A disinfecting mouth-wash 
is made by digesting three drachms of chloride of lime in two ounces 
of distilled water, and to the filtered solution adding two ounces of 
spirit, and scenting, as with attar of roses. — (Pereira.) 



436 CLEANSING THE AIR. 



IV— CLEANSING THE AIR. 



802. It was noticed (303) that the atmosphere constantly tends to 
self-purification ; its oxygen is a universal cleanser ; it gradually but 
certainly consumes the noxious gases that are poured into it, from 
whatever source. Yet its action is slow, and it often happens that in- 
jurious exhalations are set free in such quantities, or in such confined 
spaces, as to require other and active means for their removal. Besides 
ventilation, other methods are also to some extent available for getting 
rid of atmospheric impurities, some of which will now be noticed. 
The subject of malaria, air-poisons, atmospheric infection — what they 
are, how they act, and in what manner and to what extent they are 
capable of counteraction — is yet involved in much obscurity. The 
substances which relieve us of disagreeable odors and noxious emana- 
tions are numerous, and take effect in various ways. 

803. Palliatives and Disgnisers. — "When atmospheric impurities report 
themselves to the olfactory sense, they are pretty sure to receive at- 
tention, though we too often seek only relief from the disagreeable 
smell. This is done, not by removing it, but by smothering or over- 
powering it with sweet scents. "With musk, attar of roses, lavender, 
odoriferous gums, fragrant spices, aromatic vinegars, &c., a cloud of 
perfume is raised which masks the unwholesome odor. This may bo 
often an excusable resort, but it is too frequently a slovenly expedient 
to conceal the effects of uncleanliness. " They are the only resources 
in rude and dirty times against the offensive emanations from decay- 
ing animal and vegetable substances, from undrained and untidy dwell- 
ings, from unclean clothes, from ill- washed skins and ill-used stom- 
achs. The scented handkerchief in these cases takes the place of the 
sponge and the shower-bath, the pastile hides the want of ventillation, 
the attar of roses seems to render the scavenger unnecessary, and a 
eprinkling of musk sets all other stenches and smells at defiance. The 
fiercest demand for the luxury of civilized perfumes may exist where 
the disregard of healthy cleanliness is the greatest." In this connexion 
we may mention those agencies which exert a palliative effect, remov- 
ing rather than concealing or destroying the offensive bodies. Thus, 
sulphuretted hydrogen, the gas of rotten eggs, and which is copiously 
Bet free from putrefying animal bodies, may be absorbed by water, but 
the water does not decompose or neutralize it ; if heated, it all escapes 
back again into the air. The moist soil also acts as an absorbent of 
bad gases, fixing and retaining them during cold and wet weather, and 
setting them free during drought or heat. 



ACmON OP LIME AND CHLOEINK. 43? 

804. Action of Disinfectants. — A large number of Bnbstances have 
been discovered wliich destroy evil odors and injurious gases. These 
are termed disinfectants, and act chemically either to decompose the 
noxious substances or to combine with them, producing new and harm- 
less compounds. 

805. Freshly Earned Lime — Qnicklime. — Lime newly burned, caustic 
and hydrated (slaked), is used to purify the air. It has a powerful at- 
traction for carbonic acid, half a cubic foot of it absorbing nearly 40 
cubic feet of the gas. A few lbs. of it placed upon a board or tray in 
the bed-room, or oftentimes in the sick-room, rapidly absorbs this de- 
leterious substance, while the condensed gas is immediately replaced 
by an equal volume of fresh air from without. The OLly inconve- 
nience is, that as the lime combines with the acid, the water used in 
slaking is set free, which charges the air with aqueous vapor. The in- 
habitants of newly built houses, and even after a considerable time, 
often experience a similar annoyance. It is not from the ordinary 
wetness of new walls that the moisture proceeds, but from the dry 
hydrate of lime in the mortar. The carbonic acid of the room, from 
the lungs of its inmates, gradually penetrates the plaster and displaces 
this water. When quicklime is strewed over fresh animal and vegeta- 
ble substances, it I'etards their decay, and so influences the changes 
that ammonia and other volatile and strong-smelling compounds are 
less freely produced. If spread upon putrefying refuse, it acts differ- 
ently, seizing upon the acids and setting free the pungent gaseous alka- 
lies. It at first liberates a large amount of offensive gaseous matter, 
and then checks the decomposition. 

806. Chlorine as a Disinfectant. — But the most powerful disinfecting 
agent is chlorine gaa^ one of the elements of common salt (590). It is 
an energetic chemical agent, used for the destruction of coloring mat- 
ters, as in bleaching cotton, linen, fatty substances, &c. The remark- 
able hghtness and tenuity of hydrogen have been referred to (76). It 
combines with many heavier elements, forming compounds of extreme 
volatility, lighter than the air, and which constantly ascend into it. 
It is this highly rarefied gas which seems to stand closest upon the bor- 
ders of nothing, — but becomes potent through its very nothingness, 
that gives wing to the deadly exhalations, lifting them away from the 
ground into the breathing region. The gaseous poisons of the air, so 
far as known, are compounds of hydrogen. For this substance chlo- 
rine has a strong attraction, decomposing and destroying its com- 
pounds, and being a gas, it may also diftuse through the air, and thus 
cleanse and disinfect it. 



438 CLEANSING THE AIK. 

807. Forms of its use— Chloride of Lime. — Chlorine gas may be set 

fire iu tvfo yvajs: Jirst, by pouring hydrochloric acid upon finely 
po^Ydered black oxide of manganese ; and seco7id, by pouring sul- 
phuric acid upon a mixture of common salt with the same oxide. 
Chlorine stands first as a disinfectant. It is cheap, easily prepared, 
acts efliciently though diluted with much air, and in this state of dilu- 
tion is breathable without injury even by the sick. It corrodes me- 
tallic substances, which shoiJd therefore be removed as far as possi- 
ble from apartments in which it is to be used. (Other disinfecting 
gases are liable to the same objection.) If it be desired to generate 
large quantities of chlorine, the methods just mentioned maybe re- 
sorted to, but apartments cannot then be occupied^ as chlorine in any 
considerable amount is to a high degree irritating and inflammatory to 
the throat and air passages. In all common cases chloride of lime 
may be employed. This is lime charged with chlorine gas, whicli 
combines with it so easily that it is slowly set free when exposed to 
the air. It has a double action : the lime combines with all acid 
bodies as carbonic acid, sulphuretted hydrogen, while chlorine 
diffuses through the air, decomposing all the noxious compounds of 
hydrogen. It may be spread upon any putrefying substance, when it 
destroys noxious bodies as they are formed. It may be placed in a 
room, when carbonic acid slowly combines with the lime, and the 
chlorine is gradually set free. It may be dissolved in water and 
sprinkled througli bad smelling apartments, or cloths dipped in a 
diluted solution of it can be hungup in the room. After infectious 
diseases, a weak solution of chloride of lime should be sprinkled over 
sheets and family linen before washing, and the walls of the room 
washed down with it. Chloride of soda is used in the same manner 
as chloride of lime. 

808. Disinfection by Snlphnrons icid. — When sulphur is burned in 
the open air, oxygen combines with it, producing suljjliuroits acid gas. 
It has a noxious odor, and if largely mingled with the air, is 
injurious to health. It is an active chemical agent, much used for 
bleaching, as may be illustrated by holding over a burning sulphur 
match, a red rose, which is immediately whitened. Woollen, silk, and 
other garments are bleached by it. It is of a strongly acid nature and 
combines with alkaline vapors of the air, while it decomposes and de- 
stroys other substances, as sulphuretted and phosphuretted hydrogen. 
When an apartment is fumigated by burning sulphur, it is necessary 
to leave it ; it corrodes metals. 

809. Otiier Substances used for Disinfection. — Chloride of iron is a 



CHAECOAL HASTKNS CHANGE OF MATTER. 43& 

cheap aud efiicient disinfectant, though it imparts a brown or bluish 
stain wherever its solution falls. Chloride of zinc is equally eflicient, 
but more expensive. Sulphate of iron (copperas or green vitriol) haa 
strong disinfecting power. Either of these substances dissolved in 
water, (one, two, or three lbs. to the pailful,) thrown into vaults, cess- 
pools, or gutters, or over any foul masses of fermenting matter, exert 
not only a disinfecting and deodorizing action, but partially arrest 
putrefactive change. Acetate and nitrate of lead are strong disin- 
fectants. These substances are all solids. They do not assume the 
gaseous form, but act, dissolved in water, by fixation of i: xious sub- 
stances as they are set free. 

810. Effects of Cliarcoal. — It is well known that charcoal is a power- 
ful deodorizer. Strewn over heaps of decomposing filth, or the bodies 
of dead animals, it prevents the escape of effluvia. Tainted meat sur- 
rounded with it, becomes sweetened. Foul water strained through it 
is purified. Placed in shallow trays in apartments where the air is 
offensive, it quickly restores it to sweetness, and even purges the putrid 
air of dissecting rooms. Charcoal has also a powerful attraction for 
coloring substances, and is used for bleaching sirups, liquors, &c., by 
filtration through it. 

811. Mode of Action of Charcoal. — Charcoal produces these effects in 
a particular manner, unlike any substance that has been noticed. 
Most, if not aU porous solids, have the power of absorbing and con- 
densing gases within their minute interior spaces. Charcoal is ex- 
ceedingly porous, and has this property pre-eminently. A cubic inch 
of freshly burned, light, wood charcoal, will absorb nearly 100 inches 
of gaseous ammonia ; 50 or 60 of sulphuretted hydrogen, and nearly 
10 of oxygen. The charcoals are not all alike in efficacy. Animal 
cliarcoal — from charred animal substances — aud peat charcoal, arc 
both superior in absorbing and condensing power to wood charcoal. 
But how d oes this substance produce its effects ? It was formerly 
supposed, simply by sponging up the deleterious gases and retaining 
them in its pores. But later inquiries have thrown light upon this 
matter, and we now understand that by means of this mechanical 
condensation, charcoal becomes a powerful agent of destructive change. 
Chemical action is hastened in proportion to the nearness with which 
the atoms can be brought together. In the pores of the coal they are 
forced into such close proximity, as rapidly to augment the chemical 
changes. The condensed oxygen seizes upon the other gases present, 
producing new compounds, oxidized products. In this way ammonia 
is changed to nitric acid, and sulphuretted hydrogen to sulphuric acid, 



440 



CLEANSETG TUIi AIR. 



In this way, charcoal promotes oxidation, so that instead of being ac 
antiseptic or preventer of change, it is really an accelerator of decom- 
position.* This active property of hastening decomposition has been 
made medically available in the form of poultice, to corrode away 
sloughing and gangrenous flesh in malignant wounds and sores. Dr. 
Bird, in his work on the medical uses of charcoal, quotes several cases: 
we give one. " A man was admitted to St. Mary's hospital with a slough- 
ing sore upon his leg. A poultice of this kind was put on, and in six 
hours the dead portion Avas reduced in size fully one-quarter. At the 
same time, the poultice thus made, effectually prevents any odor or 
putrefying exhalations proceeding from the slough and pervading the 
apartment." Dr. Stesthouse, who, in 1855, first drew distinct atten- 
tion to the fact, that charcoal is rather a hastener of decomposition 
than an antiseptic, has contrived ventilating arrangements in which the 
air of dwellings is filtered through charcoal. He has also a breath-filter 
or respirator, consisting of a hollow case of fine flexible wire-gauze, 
which is mounted upon the face, as 
shown in Fig. 130. It is filled with 
coarsely powdered charcoal, so that all 
the air that enters the lungs is strained of 
its impurities. Charcoal is thi»i strongly 
commended as a disinfectant. It has 
many advantages over the preparations 
of chlorine, as it neither injures the 
texture of substances, nor corrodes 
metals, nor discharges the color of 
fabrics by contact, nor gives oft" dis- 
agreeable fumes. It is never in anj 
application or use, poisonous or danger- 
ous, but is entirely innocent, and in only one solitary instance can it 
become pernicious, and that is when it ceases to become charcoal, and 
is burnt in a perfectly closed room. 




* " I took the body of an English terrier, weight about ten lbs., placed tt on a stone 
door in a small apartment, and lightly covered It with charcoal ; although the weather 
was very warm, not the slightest odor could be detected. By some accident the charcoal 
was disturbed, and a large portion of the mass was left uncovered ; in spite of this tho 
circumjacent charcoal was sufficient to prevent any offensive stench. Upon seeing this, 
I left the body completely uncovered, merely surrounding it with the deodorizing agent; 
this again prevented any disagreeable smell. Having determined this fact, I again cov- 
ered the carcass. In less than a fortnight not a particle of flesh remained upon the 
bones, which were picked perfectly clean, an-i were of a sno^yy whiteness." — (Bibq oh 
Charcoal.) 



POISONS, AND THEIR ANTIDOTES. 441 

v.— POISONS. 

812. Poisons and Poisoning. — Poisons are divided into three classes 
according to the way they act upon the system. Acrid or irritant 
poisons directly corrode or destroy the tissues with which they come 
in contact, and cause intense pain, hut do not suspend consciousness. 
Strong acids, and alkalies, and indeed all poisonous metallic substances, 
belong to this class. Narcotic poisons are such as produce stupor, as 
opium, carbonic acid. Narcoto-acrids, as tobacco, alcohol, &c., act 
both as acrids and narcotics. Some of these poisons may be arrested 
or neutralized in the system before producing fatal results, if measures 
are promptly taken, but no time is to be lost. "Whatever is done, 
must be done at once ; the delay necessary to ransack books for anti- 
dotes, or to get a physician, may cost the victim's life. If sevtre pain 
in the stomach, vomiting, purging, &c., come on after a nieal, poisoning 
is to be suspected. Something may be gathered from the demeanor 
of the poisoned individual, and a knowledge of circumstances. A 
person who has swallowed poison, by way of suicide, will be apt to 
be more silent about it than one who ha-s taken it accidentally or to 
whom it has been administered purposely. 

813. Resonrces in case of Poisoning. — If the vial or vessel from 
which the poison was taken be accessible, or if there be discolored 
spots upon the dress, and if on applying the tongue to eitlier there is 
sourness, we infer that the poison is acid. In this case, or if it bo 
known that an acid has been swallowed, chalk or whiting, mixed with 
milk, should be given copiously. If these are not at hand, plaster torn 
from the wall, or soap, may be substituted. Alkalies are given as an- 
tidotes to acids, and the reverse. Thus, poisoning by oxalic or sul- 
phuric acids may be remedied by soda or saleratus, while poisoning by 
pearlash would be arrested by vinegar. So if lime get into the eyes, 
it may be dissolved and washed out by moderately strong vinegar. 
The antidote for corrosive sublimate is eggs; for sugar of lead, epsom 
salts. If other or unknown poisons have been taken, the stomach 
should be freed of its contents as speedily as possible by an emetic, the 
readiest and best being a teaspoonful of mustard stin-ed up with 
warm water, its action being promoted by copious draughts of the 
latter. The poison called arsenic or ratsiane is not the metal arsenic, 
but the oxide of arsenic — a white, slightly sweetish insoluble powder. 
Being destitute of any decided taste, it is eminently fitted for the pui*- 
pose of the poisoner, as it may be mingled witli food without easy 
detection. But while this circumstance is fitted to tempt the mur- 

19* 



442 AESENIC POISONING. 

derer, there follows another which is fraught with sure retrihution 
No poison is so ready and certain of detection as arsenic. And not 
only this, but " it is as indestructible as adamant. The corpse may 
decay ; the coffin fall to dust ; hundreds or thousands of years may 
pass, but underneath the mound of earth, in the spot where the 
corpse was laid, there is the arsenic." The best antidote to this poison 
is the hydrated sesquioxideof iron, which combines with it, forming an 
inert compound ; in the absence of this, milk, sugar, eggs, &c., may 
be given, and an emetic should be administered as quickly as possible 
to relieve the stomach of its contents : it must be prompt to be 
available. 



APPENDIX. _ 



ADDITIONAL LIST OF TEMPEEATUKES. 



Lowest artificial cold 187° below zero, or 219° below freezing water 

Carbonic acid freezes 14S° below zero, or 180° below freezing water, 

Lowest natural temperature at Yakutsk, in Siberia, 84° below zero, 

Estimated mean temperature of the North Pole, 13° below zero. 

Salt water of specific gravity 1-104, and oil of turpentine freezes, 

Wine freezes, 

Blood freezes, .... 

Milk freezes, 

Water freezes, .... 

Alcohol boils in a vacuum. 

Mean winter temperature of England, 

Temperature of hybernating animals, 

Mean winter temperature at Rome, 

Mean annual temperature at Toronto, 

Putrefaction begins, . 

Cultivation of the vine begins at a mean annual temperature of, 

Mean annual temperature of New York, . 

Mean annual temperature at Eomo, 

Cultivation of the vine ends. 

Water boils in a vacuum, 

Temperature of glow-worm and cricket, 

Silk-worm hatches — temperature of germination, 

Tepid bath begins, . . . . " 

Acetous fermentation, .... 

Putrefaction rapid, .... 

Tepid bath ends, — warm bath begins, .... 

Temperature in man — blood heat, .... 

Warm bath ends, — vapor bath begins, .... 

Cold-blooded animals die, ..... 

Vapor bath ends, ..... 

Temperature in a boat in Upper Egypt, . . 

Steamboat's engine-room (West Indies), . . 

Starch converted to sugar, ..... 

Finland vapor bath, .... . 

Alcohol (specific gravity •794) boils. 

Water boils at the summit of Mont Blanc (15,360 ft. elevation). 

Water boils at an elevation of a mile, 

Water boils at the sea-level, ..... 



14' 

20' 

25" 

SO" 

32" 

36° 

87.8° 

38° 

41° 

43° 

50° 

50° 

54° 

59° 

65° 

72° 

74° 

77° 

86° 

89° 

93° 

95° 

98° 

99° 

106° 

130° 

138° 

155° 

160° 

170° 

174» 

183° 

202° 

212° 



444 



APPENDIX. 



Syrup, 52 per cent, sugar, boils, 
Water of the Dead Sea boils, 
Syrup, 80 per cent, sugar, boils, 
Gypsum converted to plaster, 



216° 
223° 
264° 
291° 



B. 



We append an illustration of the astonishing scale of minuteness upon which 
even art has found it practicable to conduct her operations. Within a circle of 
but one-thirtieth of an inch in diameter — a mere visible dot, as 
we see in the figure, M. Fromext, by an exquisite mechanical I 

contrivance, executed an elaborate piece of writing and engraving. • 

Of course no result was visible to the naked eye ; but when the 
work was placed under a compound microscope, its detaOs came 
out, as we see in fig. 131, which is a transcript of the magnified view. With 
what marvellous accuracy were those infinitesimal movements performed. 

Fig. 131. 




INDEX. 



Ablution of the face, 434. 

Acids, vegetable, 225 ; composition of, 225 ; 
of apples, 225 ; of lemons, 225 ; of grapes, 
225 ; nature of, 369. 

Acetic acid, 226. 

Air, non-conduction of, 85 ; pressure of, 43, 
151 ; composition of, 49, 153 ; contami- 
nation of by gas burning, 123 ; general 
offices of, 150 ; weight of, 151 ; effect of 
varying pressure of, 152 ; intermixture of, 
153: constituents of, 154 ; oxygen of, 154; 
moisture in, 157 ; conditions of drying 
power of, 15S ; system att'ected by moist, 
160 ; by dry, 161, 170 ; effects of its ingre- 
dients, 163; impurities of external, 165; 
conditions of salubrity, 166 ; self-purify- 
ing, 167 ; causes of impurity of in dwell- 
ings, 16S ; bad influence of heating appa- 
ratus upon, 168; affected by hot-iron sur- 
faces, 169 ; composition of, altered by 
heating, 169 ; impurities of, from the body, 
170 ; L)r. Farraday on, 171 ; of bedrooms, 
171 ; purity of the design of natui-e, 172 ; 
danger of foul, 174; contamination of, in- 
doors, ISl ; vitiated by illumination, 183; 
vitiated by the person, 1S4; influence of 
plants upon, 1S5; in motion, 1S5; cur- 
rents in close rooms, 1S6, 187; stratifica- 
tion of, in rooms, 187 ; currents through 
doors and windows, 189, 190 ; currents 
affecting the system, 191 ; supply of, by 
crevices, &c., 195 ; modes of introducing, 
196 ; effect of breathing rarified, 355. 

Albumen, vegetable, 227 ; composition of, 
227 ; properties of, 228. 

Alcohol, OS an illuminator, 116; as a pre- 
server, 311 ; the principle of spirituous 
luiuors, 378. 

Aliments, source of, 205; classification of, 
206,207; undue proportions of, 38S ; cor- 
rection of, 401. 

Alkalies, 369. 

Amaurosis, 145; subjects of, 146. 

Apartments, size of for breathing, 184. 

Appetite, regulation of, 410. 

Apples, composition of, 244 

Argand burners, 112. 

Ainutt's valve, 19S; importance of, 199. 



Arrow-root, 215. 

Arsenic, 441. 

Artificial light, 105; from ignition, 105; 
measurement of, 124 ; color of, 137 ; inju- 
rious action of, 137; how it affects the 
eyes, 139 ; effects upon the retina, 140, 
144; heat accompanying, 141; unsteadi- 
ness of, 142; extraneous rays, 143 ; may 
produce inflammation, 144 ; management 
of, 146 ; ■whitening by absorption, 148. 

B 

Barley, 240. 

Barometer, 4-3. 

Beans, composition, 242 ; mineral matter 
in, 243 ; digestibility of, 390. 

Beaumont, Ur's. table, 343. 

Bedrooms, air of, 171 ; ventilation of, 201. 

Beets, 247. 

Beverages, 2S9. 

Blood, constituents of, 250, 347; globules, 
347; alkaline, 370. 

Boiling, culinary changes by, 277. 

Boiling point, elevation of, 44. 

Bran, composition of 235. 

Brain, measure of its change, 865; plios- 
phatic constituents of, 366 ; has its specHI 
nutriments, 367 ; excitants, 369. 

Braziers, 61, 62. 

Bread, from plain flour and water, 258 ; fer- 
mented, 259 ; objections to fermented, 
267 ; unfermented, 268 ; raised by chemi- 
cals, 269, 270 ; heat of baking, 271 ; loss of 
■weight in baking, 272; changes in the 
crust, 272 ; in the crumb, 272 ; moisture 
in, 273: good, 273; influence of salt on, 
274; alum, 274; effects of lime water, 
275; different kinds of, 276; white and 
brown, 277 ; coarse and fine, effects of, 389. 

Broth for the sick, 284. 

Buckwheat, composition of, 241. 

Burning fluids, composition of, 116; how 
explosive, 110; conditions of accident 
from, 117 ; how used with safety, 117. 

Butter, separation, of, 285; compo.>-ilion and 
properties of, 286; cauae of its change- 
ableness, 315 ; cause of r»nciJily,?><J; ac- 
tion of air upon, 316; nub^tancef unat to 
preserve, 317. 



446 



c 

Cabbage, nutritive properties of, 241. 

Caiupiifiie, 115; combustion of, 115 ; why It 
spoils, 115. 

Candles. loS; stearic acid, 109; tallow, 109; 
speruiaceti and wa.x, 109 ; structure of, 
110; office of wick, 110; bow it burns, 
110; snuffing of. 111; shade for, 143. 

Carbon, office in fuel, 49; heating effects 
of, 51. 

Carbonic acid, 161 ; physiological effects of, 
102; in small quantities, 102; case of sui- 
cide by, 102; necessity for, in air, 163; 
exhaled by respiration, 1S2. 

Carrots, 248. 

Casein, composition of, 228, 

Cataract, 136. 

Cellars, foul air in, 173. 

Changes In the living system, 326 ; rate of, 
327; equ.ilization of bodily, 362; hasten- 
ing and retarding, 303. 

Charcoal, as fuel, 53 ; as a disinfectant, 439 ; 
mode of its action, 439; respirator, 440. 

Cheese, preparation of, 2SS; changes by 
time, 317; influence in digestion, 391. 

Chevreul, 91. 

Chimneys, draught of, 55 ; causes of smoky, 
56, 57, 58, 59 ; currents in summer, 200. 

■)hocolate, 29S ; adulterations, 300 ; effects, 
373. 
'holera and foul air, 175. 

Jhurning, 285. 

Citric acid, 225. 

Cleansing, principles involved in, 422 ; by 
alkaline substances, 425; of te.xtile arti- 
cles, 428; cottons, linens, and woolltu?, 
429; of spots and stains, 430; agents for, 
430; of the person, 431 ; of the skin, 433; 
of the face, 434; of the teeth, 435; of the 
air, 43G. 

Climate, artificial, 22. 

Coal, mineral, 53, 54. 

Cocoa, composition, 29S ; preparation, 299 ; 
how used, 299. 

Coffee, varieties, 294; composition, 294; 
effects of roasting, 295; effects of time 
upon, 296 ; mode of preparation, 297 ; adul- 
teration, 297 ; how detected, 298 ; Lehman 
on the effects of, 378. 

Cold, when most fatal, 35S. 

Color, influence upon radiation, 30; upon 
absorption, 31 ; Newton's theory of, 89 ; 
Brewster's theory, 89 ; complementary, 
90; tints and tones of, 91 ; chromatic cir- 
cles, 92 ; contrast of, 97 ; mutually inju- 
rious, 98; contrast of tone, 99 ; harmonies 
of, 100 ; circumstances influencing, 101 ; 
associated with white, black, gray, 101 ; 
combining, 102 ; influence of, upon com- 
plexion, 102 ; arrangement of flowers, 103 ; 
paper-hangings, 103; furniture, 106; popu- 
lar recognition of the effects of, 140 ; asso- 
ciated heat of, 141. 
Combustion, products of, 50; air hinders, 

55 ; within the body, 851. 
Common salt transparent to heat, 23 ; effect 
upon bread, 274; uses of, in the system, 
871; contained in food, 372; mode of crys- 
tallization, 311 ; purilication of, 312; liow 
it preserves meat, 312; how it injures 
meat, 313; too little aud too much, 377. 



Complexion, 102. 

Condiments, 391. 

Contagion and foul air, 175. 

Corn starch, 215. 

Cream, production of, 253. 

Culinary art, objects of, 256. 

Culinarv utensils, 318; of iron, SIS; of tin, 
319 ; zinc, 320 ; copper, 820, 821 ; enam- 
elled ironware, 321; earthenware, 322; 
Porcelain ware, 323. 

D 

Dentifric<6, 435. 

Dew, cause of, 32 ; dew-point, 153. 

Diet, for brain-workers, 368; mixed indis- 
pensiible, 393; exclusive meat, bad econ- 
omy, 396; required by chilarezi, 402; oJ 
flesh, influence of, 405; mineral matters 
replacable In, 406 ; economy of vegetable 
and animal, 407 ; diversities of, 408, 409 ; 
scale of U. S. Navy, 410, and the capacity 
of exertion, 415 ; order and variety in, 
416, and corpulence, 417; of infancy, 417, 
418; of childhood and youth, 419; ot 
middle life, 420; of advanced life, 420. 

Diffusion of gases, 153. 

Digestion, object of, 330; in stomach, 3.3S; 
extent of gastric, 340; influence of coffee 
on, 877. 

Dirt, composition of, 423. 

Disguising bad smells, 436. 

Disinfectants, 437 ; quicklime, 437 ; chlorine, 
437; chloride of lime, 433; sulphurous 
acid, 438 : charcoal, 439. 

Double windows, 159. 

Dough, water absorbed by, 257; eftects of 
kneading, 25s; what makes it ri.se, 261; 
raising by leaven, 262 ; raised by yeast, 
266; acidity in, 266; sugar in, 267; alco- 
hol in, 267 ; raised Avith esgs, 270. 

Dress, 21, 85 ; colors of, 102.- 

E 

Ebullition, 42 ; effects of pressure upon, 44. 

Egss, composition of, 250; preservation of, 
318. 

Electricity, atmospheric, 164. 

Emerson's injector, 197 ; ejector, 193. 

Ether, luminous, vibrations of, 87. 

Evaporation, 42 ; cooling etiects of, 46 ; rate 
of, 159. 

Eye, sensibility to colors, 97 ; parts of, 127, 
128 ; minuteness of images in, 129 ; adap- 
tation to light, 130 ; affected by conditions 
of the system, 130 ; influence of reading 
and writing ui)on, 131 ; cause of far-sight- 
ed, 132; remedy of far-sightedness, 133; 
cause of near-sighted, 134; remedy of 
near-sighted, 135; cataract in, 136; influ- 
ence of carbonic acid upon, 142 ; bad light 
inflames, 144. 



Faraday, Dr., 171. 

Fats, see Oils. 

Farina, 237. 

Farina kettle, 45. 

Fermentation, 260 ; conditions of, 260; dlf 

ferent kinds of, 260 ; sjiontaneous, 260. 
Fibrin, 228. 



INDEX. 



44' 



Fire, kindling of, 50 ; risk of, 73 ; origin 
of, "i. 

Fireplace, form of, 62 ; action of, 62 ; econ- 
omy of, 63; ventilation by, 192. 

Flame, cause of, 50 ; illim ination from, 106 ; 
hoUowness of. 111) ; length of, in gas burn- 
ing, 123. 

Flesh, composition of, 2-lS; juice of, 249; 
action of heat upon, 281 ; changes by 
cooking, 2S2; loss of weight in, 2b2; best 
plan of cooking, 2S3 ; common method 
objectionable, 2S3 ; its juices acid, 371 ; 
digestion of, 3SS. 

Flour, white and dark, 236; evaporation 
from, 236 ; changes in, 236 ; effects of its 
preparations, 3S9. 

Foods, why perishable, 300 ; conditions of 
perishableness, 301 ; effects of, may be un- 
derstood, 325 ; periodic supply of, 337 ; 
digestibility of, 341, 342, 343 ; changes in 
mouth, 330 ; in stomach, 335 ; in intes- 
tines, 344 ; constipating and laxative, 346; 
final destination of, 347 ; produced by 
forces, 34S ; produces animal force, 349 ; 
unequal combustibility of, 351 ; heat-pro- 
ducing and tissue-making, 352 ; replaced 
by houses and clothing, 358; ash elements 
of, 369 ; demand for variable, 408 ; daily 
requirement of, 409. 

Force, production of, destroys tissue, 361. 

Freezing, artificial, 41 ; heat produced by, 
42. 

Frost, cause of, 33. 

Fruits, composition of, 243 ; dietetic effects 
of, 391. 

Fuel, influence of, 22 ; composition of, 49 ; 
heating effects of, 54. 

Furniture, colors of, 104. 

G 

Gas fixtures, 124. 

Gas, illumination by, 119 ; sources of, 119 ; 
composition of, 120; purification of, 119; 
various sources of, 120 ; measurement of, 
121; how burned, 122; contaminations of 
air, by burning of, 123; disadvantages of 
lighting by, 124; fixtures of, 124 ; is light- 
ing by, injurious, 149. 

Gas meter, 121. 

Gastric juice, 83S ; its acid and ferment, 
339 ; quantity of, 841. 

Gelatin, 230. 

Gingerbread, 271. 

Glass, opaque to heat, 23. 

Gluten, 229 ; quality of, 232. 

Glycerine, 109. 

Grain, grinding of, 234; structure of, 234; 
sifting of, 235. 

Grates, 64; combustion in, 64; Circular, 
60 ; Arnotfs, 66 ; height of, 67. 

lium, artificial, 223; composition of, 223; 
physiological effects of, 384. 



Heat, from the sun, 18; from the stars, 18; 
distribution of, 19; influence on vegeta- 
tion, 19; distribution of auim.al, 20; in- 
fluences man's development, 20; relation 
to character, 21 ; diffusion of, 23 ; equi- 
librium of, 23 ; expansion of, 23 ; weight 
ot, 24 ; radiation of, 27, 29, 80 ; transmis- 



sion of, 2S ; absorption of, 29 ; exchanges 
of, 31 ; conduction of, 34; convection of, 
36; circulation of, 37; capacity for, 3S; 
latent, 39, 40, 41, 46; Intluenco on the 
body, 48; loss of, in rooms, 60 ; source of 
in rooms, 61 ; amount of bodily, produced, 
361). 

Heating arrangements compared, 74. 

Honey, 217. 

Hot-air furnace, 70 ; ventilation by, 193. 

Hot-water apparatus, 72. 

Human body, purpose of, 848 ; constant 
temperature of, 353; how it loses heat, 
354; how it produces heat, 854; resources 
against cold, 356 ; force exerted by, 360 ; 
limited action over food, 392 ; its restricted 
transforming power, 404. 

Hunger, use of, 329. 

Hydrogen, its office in fuel, 50; heating 
powers of, 51. 

Hydrometer, 255. 



Illumination, artificial, 105 \ by ignition, 
106 ; from burning gas, 106 ; simplio £y of 
the laws of, 107 ; by means of solids, 108 ; 
by liquids, 112 ; by gases, 119. 

Impure air, and contagion, 175 ; cholera and, 
175; fevers and, 176; scrofula and, 177; 
consumption and, 178; infant mortality 
and, 17S ; undermines the health, 179 ; 
morbid mental effects of, 180. 

Indian corn, 239. 

Intestines, juices of, 344; changes in, 345; 
absorption from, 345. 



Jelly, vegetable, 226. 

K 

Kneading, effects of, 258. 



Lactometer, 255. 

Lamps, 112 ; structure of, 113 ; astral, 113 ; 
Carcel, 114 ; .sinumbra, 113 ; hot oil, 114 : 
Newell's 117 ; study, 148. 

Language, 22. 

Lead, vessels for water, 212. 

Leaves, nutritive properties of, 244. 

Lenses, 84. 

Lettuce, 245. 

Light, exhilarating effects of, 76 ; theory of, 
77 ; diffusion of, 78 ; reflection of, 79, SO ; 
scattered by air, 82; transmission of, 82 ; 
refraction of, 82 ; wave theory of, 87 ; arti- 
ficial, 105; from ignition, 105; mciisure- 
mentof, 124; results of Ure and Kent, 126; 
color of artificial, 137; injurious action 
of artificial, 137. 

Liquefiiction, 37. 

Liquors, alcoholic, 878 ; cannot replace wa- 
ter in the system, 379, and anim.al heat, 
379; Booker's observations, 379; not eco* 
nomical, 38; stimulating effect, 380. 

Looking-glass, 79. 

Lyman's cold-air flue, 198 ; refrigenvtoJ- SOT 



Macaroni, 233. 
Malaria, 166. 



M 



i48 



Malic acid, 225. 

Mar^'aric aciil. 109. 

MMr-ariiif, l(l9. 

Mastication, importance of, 833. 

Ml'uIs, frequency in times of, 410 ; rest be- 
fore, 411 ; state of mind during, 412; e.x- 
crcise after, 412 ; effects of excess at, 41.4. 

Melting points, 38, 111. 

Milk, composition of, 250 ; qualities of, 251, 
252; cream of, 253; value of, 255; mineral 
matter in, 256; spontaneous curdling of, 
287; curdling with acids, 287; with ren- 
net, 288; i>rcserving, 814; etfeots of, 331. 

Mind, relation of, to matter, 3G4; its action 
destroys the nerves, 305 ; weara the body, 
306. 

Moisture, in air, 157; in the air of rooms, 
158 ; amount required in air, 183 ; the 
supply of, 194. 

Molasses, 221. 

M. Mouries, 277. 

Musical sounds, 85 ; scale, SO. 

N 

Night-air, 167. 

Nitrogen, 154 ; lowers the combustibility of 
food, 352. 

Nitrogenous principles, properties of, 230 ; 
names of, 281 ; destination of, 361. 

Non-nitrogenous principles, different values 
of, 395. 

Nutrition, effects of, insufficient, 414. 

Nutritive values, 895 ; scale of, .397 ; equi- 
librium of, 396; milk, 398; wheat, 399; 
adaptations of wheat, 899 ; coajse bread, 
400. 

O 

Oats, 239. 

Oils, proximate composition of, 109, 114; 
fluidity of, 114; kerosene, 118; sylvic, 
118; volatile and fixed, 223; sources of, 
223; proportion of in articles of diet, 224; 
ultimate composition of, 224; supply of, 
in diet, 384; accumulation of, 384; in 
stomach, 385; digestibility of, 386; rela- 
tion of to nutrition, 387 ; to consumption, 
387. 

Olcaic acid, 109. 

Oleaine, 109. 

Onions, 247. 

Oxygen, 49, 154 ; how it enters tie system, 
155 ; what it does in the body, 156 ; effect 
of varying the quantity of, respired, 157; 
consumed by respiration, 181; consumed 
by combustion, 182; an exciter of decay, 
802; destructive agency o^ 350; action 
of, upon tissues, 862. 

Oxalic acid, 226. 

Ozone, 164. 

r 

Paper-liangings, colors of, 103; poisonous 
colors on, 173. 

Parr. Thomas, 823. 

Parsnips, 248. 

I'eutic acid, 226. 

Peas, composition, 241 ; digestibility of, 390 

Photometer, 125. 

Pictures, h.inging of, 81 ; frames of, 104. 

Poisons, usedto color candy, 222 ; how di- 
vided, 441 ■ how managed, 441. 



Pot.itoes, composition of, 245 ; water in, 245 
starch in, 246; nutritive part of, 246 ; dry 
matter of, 246; ash of, 247; changed by 
cooking, 280. 

Potash, 374. 

Preservation, by exclusion of air, 802 ; Ap- 
pert's method, 303; in canisters, 304; in 
Spratfs cans, 305 ; at low temperatures, 
806; by freezing, 806; in refricerators, 
307 ; fruits, 308 ; by drying, 309 ; "by anti- 
septics, 311 ; by sugar, 313 ; by alcohol, 314. 

Putrefaction, 259. 

E 

Reflectors, 146; blue, 147. 
Retina, imago formed upon, 129 ; loss of sen- 
sibility of, 144; paralysis of, 145. 
Rice, composition of, 241. 
Roots edible, dietetic effects of, 391. 
Rye, anatomy of, 235 ; compositioD of, 2.'J8. 



Sago, 215. 

Saliva, flow of, 331 ; properties of, 332 ; uses 
of, 332 ; action in stomach, 340. 

Salts, 369. 

Shades, ground glas.s, 146 ; blue, 147 ; struc- 
ture and mounting of, 147. 

Simultaneous contrast of colors, 97. 

Skin, structure of, 431; impurities of, 432; 
cleansing of, 433. 

Smoke, 59, CO. 

Soap, how made, 425 ; hard and soft, 426 ; 
water in, 426 ; varieties of^ 427 ; its re- 
action with water, 428. 

Soda, 374. 

Solution, 208. 

Sound, transmission of, 85. 

Soup, preparation and properties of, 234 ; 
effects of, 381. 

Spectacles, 131; for the far-sighted, 183; 
for the near-sighted, 1.35 ; suggestions in 
selecting, 136; man.igement, 187; pebble- 
glass, 187 ; colored glasses for, 148. 

Spectrum, 88. 

Spcciflc heat, 38. 

Spermaceti, 109. 

Spitting, effects of, 334. 

Starch, separation of, 213 ; proportion of, 
214; grains, 214; sago, 215; tapioca, 215; 
arrow-root, 215 ; corn-starch, 215 ; com- 
position, 216; culinary changes of, 279; 
physiological effects of, 388. 

Steam, warming by, 73. 

Stearine, 109. 

Stearic acid, 109. 

Stomach, figure of, 335; layers of, 335; mo- 
tions of, 886 ; follicles of, 836 ; absorption 
from, 846. 

Stovepijie, 69. 

Stove, Franklin, 64; self-regulating, 68; air- 
tight, 68; best, 69; ventilation by, 19.3. 

Sugar, proportion from various sources, 216; 
artilicially produced, 216; honey, 217; 
cane,21S; grape,21S; sweetening power, 
218; production of brown, 219; compo- 
sition of brown, 219 ; fermentation of 
brown, 220 ; contaminations of brown, 
220 ; refined, 221 ; candy, 221 ; culinary 
changes of, 278 ; as a preserver, 313 ; phy 
Biological effects of, 383; reflning of, 44. 



INDEX. 



440 



Tapioca, 215. 

Tartaric acid, 225. 

Tea, 2S9; the shrub, 289; varieties, 2Si) ; 
green and black, 290 ; composition of, 291 ; 
how best made, 292 ; grounds, 292 ; adul- 
teration, 293 ; physiological elfects of, 377. 

Teeth, 321 ; cleansing of, 435. 

Temperature, facts of, 27 ; of body constant, 
353 ; regulation of bodily, 357 ; diet and 
dallv changes of, 359. 

Therinometer, 23, 24, 25, 26. 

Turpentine, spirits of, 115. 

Turnips, 24S. 



Vegetables, influence of, iu diet, 390. 

Vegetarian question, 402 ; statements of, 
contrasted, 403, 404. 

Ventiducts, 198. 

Vermicelli, 2«;3. 

Vinegar, effects of, 393. 

Vision, conditions of. 76; value of the sense 
of, 126 ; how produced, 129 ; mechanism 
of, 128 ; optical defects of, 131 ; limits of 
perfect, 131 ; paralysis of the nerve of, 145. 

Ventilation, of the person, 186 ; arrange- 
ments for, 192 ; by the fireplace, 192 ; by 
stoves, 193 ; by hot-air arrangements, 193 ; 
points to be secured in, 196 ; downward 
current in, 197 ; ascending current in, 198 ; 
by an additional flue, 200 ; of gas-burners, 
201; of cellars, 202; should be provided 
for in building, 202 : involves loss of heat, 
SU8. 



Warming by steam, 73; by hot water, 72; 
and ventilation best method of, 195. 

Warming of rooms by air, 71. 

Waste and supply, 228. 

Water, its relations to heat, 39 ; evaporation 
of, 42 ; boiling of, 42, 43 ; spheroidal state 
of, 44 ; solvent powers of, 207 ; to hasten 
solution, 208 ; its dissolved gases, 208, 209 ; 
varieties of, 208; rain and snow, 209; or- 
ganic contaminations of, 209; living in- 
habitants of, 210 ; their use, 210 ; its min- 
eral matter, 211; hard and soft, 212; in 
contact with lead, 212 ; supply of rain, 
213 : for culinary uses, 280 ; physiological 
effects of, 374, 375 ; influences digestion, 
375 ; change of tissue, 376 ; proportions of 
in foods, 894; as a cleansing agent, 422; 
filtration of, 423 ; its dissolved impurities, 
424. 

Wave movements, 84 

Wax, 109. 

Wheat, composition of, 232 ; gluten in, 2.33 
water in, 233; mineral matter in, 237 
nutritive value of, 399. 

Wood, water in, 51 ; heating value ef, 52 
soft and hard, 52. 

Woody fibre, 278. 



Yeast, brewer's, 262; a plant, 263; Qomcstic 
preparation of, 264; hops in, 265; drying 
of, 265 ; bitterness o^ 26C ; acidity ot, 
396. 



TESTIMONIALS. 



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From, the Scientific American. 
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nf the learner aids his memory; and as the eye, In regard to all objects bav 



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